Android基础之再回顾

来源：互联网发布：广联达计价软件编辑：程序博客网时间：2024/05/22 00:12

找个工作好难啊，我就想找个实习，挣点学费有这么难吗？面试公司问我源码，几个月以前学过的东西，哪还记得啊。。。让我看看代码我还能写出来，直接问我那记得起来。都是程序员，给老板打工的，何必这么为难呢，你直接给我个任务，我能完成，你多多考虑下，完不成，我自己走人，再说我只是想找实习啊。唉，只是发发牢骚，不能怪公司，只能说自己没学好，还是回顾一下吧。

1、Activity的生命周期

我们都知道activity的生命周期有七个，并且知道它们的作用，但是当一个activity中点击一个按钮启动另一个activity，并且在第二个activity按下back键时，这两个activity的生命周期是怎么运行的？
设第一个activity为A，第二个activity为B,则以下为他们的执行顺序：

ActivityA: ------------------onCreateActivityA: ------------------onStartActivityA: ------------------onResumeActivityA: ------------------onPauseActivityB: ------------------onCreateActivityB: ------------------onStartActivityB: ------------------onResumeActivityA: ------------------onStopActivityB: ------------------onPauseActivityA: ------------------onRestartActivityA: ------------------onStartActivityA: ------------------onResumeActivityB: ------------------onStopActivityB: ------------------onDestroy

2、Service的启动方式

现在有俩个activity，一个服务。
那么以下几个过程是怎么样的？
先看代码。

第一个activity

public class ActivityA extends AppCompatActivity {    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        TextView textView = (TextView) findViewById(R.id.helloword);        Intent intent = new Intent(ActivityA.this, TheService.class);        startService(intent);        textView.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                Intent intent = new Intent(ActivityA.this,ActivityB.class);                startActivity(intent);            }        });//        Log.d("ActivityA","------------------onCreate");    }    @Override    protected void onStart() {        super.onStart();//        Log.d("ActivityA","------------------onStart");    }    @Override    protected void onPause() {        super.onPause();//        Log.d("ActivityA","------------------onPause");    }    @Override    protected void onStop() {        super.onStop();//        Log.d("ActivityA","------------------onStop");    }    @Override    protected void onDestroy() {        super.onDestroy();//        Log.d("ActivityA","------------------onDestroy");    }    @Override    protected void onResume() {        super.onResume();//        Log.d("ActivityA","------------------onResume");    }    @Override    protected void onRestart() {        super.onRestart();//        Log.d("ActivityA","------------------onRestart");    }}

第二个activity

public class ActivityB extends AppCompatActivity {    ServiceConnection sc = new ServiceConnection() {        @Override        public void onServiceConnected(ComponentName name, IBinder service) {            TheService.MyServiceBinder myServiceBinder = (TheService.MyServiceBinder) service;            TheService theService = myServiceBinder.getService();        }        @Override        public void onServiceDisconnected(ComponentName name) {        }    };    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_b);        TextView textView = (TextView) findViewById(R.id.thissssss);        textView.setText("fffffffffffffffffff");        textView.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                Intent intent = new Intent(ActivityB.this,TheService.class);                stopService(intent);            }        });//        Log.d("ActivityB","------------------onCreate");        Intent intent = new Intent(ActivityB.this, TheService.class);        bindService(intent, sc,BIND_AUTO_CREATE);    }    @Override    protected void onStart() {        super.onStart();//        Log.d("ActivityB","------------------onStart");    }    @Override    protected void onPause() {        super.onPause();//        Log.d("ActivityB","------------------onPause");    }    @Override    protected void onStop() {        super.onStop();//        Log.d("ActivityB","------------------onStop");    }    @Override    protected void onDestroy() {        super.onDestroy();//        Log.d("ActivityB","------------------onDestroy");        Intent intent = new Intent(ActivityB.this, TheService.class);        unbindService(sc);    }    @Override    protected void onResume() {        super.onResume();//        Log.d("ActivityB","------------------onResume");    }    @Override    protected void onRestart() {        super.onRestart();//        Log.d("ActivityB","------------------onRestart");    }}

服务

public class TheService extends Service{    private MyServiceBinder myServiceBinder;    @Override    public void onCreate() {        super.onCreate();        Log.e("TheService","--------------onCreate");        myServiceBinder = new MyServiceBinder();    }    @Override    public int onStartCommand(Intent intent, int flags, int startId) {        Log.e("TheService","--------------onStartCommand");        return super.onStartCommand(intent, flags, startId);    }    @Override    public void onDestroy() {        Log.e("TheService","--------------onDestroy");        super.onDestroy();    }    @Nullable    @Override    public IBinder onBind(Intent intent) {        Log.e("TheService","--------------onBind");        return myServiceBinder;    }    @Override    public boolean onUnbind(Intent intent) {        Log.e("TheService","--------------onUnbind");        return super.onUnbind(intent);    }    public class MyServiceBinder extends Binder {        public TheService getService(){            return TheService.this;        }    }}

第一个方式：直接先打开第一个activity，然后打开第二个activity，并且在第二个activity打开后直接按下back键，返回到第一个界面后再按下back键，退出应用。

打开Aactivity：

TheService: --------------onCreateTheService: --------------onStartCommand

打开BActivity

TheService: --------------onBind

按下back键

TheService: --------------onUnbind

退出应用程序什么都不会打印。
看应用管理器，服务还在运行，强制结束后，打印：

TheService: --------------onDestroy

服务结束

第二个方式，打开应用，然后直接打开第二个界面，并且点击按钮调用stopService，然后按下back键，最后结束应用。
打开应用：

TheService: --------------onCreateTheService: --------------onStartCommand

打开第二个界面

TheService: --------------onBind

点击textview什么都不会发生，按下back键后。

TheService: --------------onUnbindTheService: --------------onDestroy

服务已经结束

第三个方式，按照第一种方式操作直到退出应用，不去应用管理器关服务，而是直接打开应用。

打开Aactivity：

TheService: --------------onCreateTheService: --------------onStartCommand

打开BActivity

TheService: --------------onBind

按下back键

TheService: --------------onUnbind

退出应用程序没有打印。
重启应用

TheService: --------------onStartCommand

3、Fragment的创建

我所用到的有三种方式：

1、第一种

首先定义一个类：

import android.app.Activity;import android.os.Bundle;import android.support.annotation.Nullable;import android.support.v4.app.Fragment;import android.util.Log;import android.view.LayoutInflater;import android.view.View;import android.view.ViewGroup;import com.example.houjie.studyapk.R;public class LifecycleFragment extends Fragment{    private  final String TAG ="LifecycleFragment";    @Nullable    @Override    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {        Log.i(TAG,"Fragment onCreateView");        return inflater.inflate(R.layout.layout_only_textview,null);    }}

在这儿返回一个只有textview的LinearLayout

xml中直接定义Fragment

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical"    tools:context="com.example.houjie.studyapk.studyfragment.fragment.LifecycleActivity">    <Button        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="清除Fragment"        android:id="@+id/FragmentBtnClear"        />    <Button        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="创建Fragment"        android:id="@+id/FragmentBtnCreate"        />    <fragment        android:layout_width="wrap_content"        android:layout_height="wrap_content"        class="com.example.houjie.studyapk.studyfragment.fragment.LifecycleFragment"        android:id="@+id/Fragmentfragment">        <TextView            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:text="nihao"        />    </fragment></LinearLayout>

定义fragment，用class属性声明，这里必须要包的绝对路径
声明好了就是使用

public class LifecycleActivity extends AppCompatActivity {    private final String TAG ="LifecycleActivity";    private FragmentManager fragmentManager;    private Button button1;    private Button button2;    private LifecycleFragment lifecycleFragment;    private int page;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_fragment_lifecycle);        Log.i(TAG,"Activity onCreate");        button1= (Button) findViewById(R.id.FragmentBtnClear);        button2= (Button) findViewById(R.id.FragmentBtnCreate);        fragmentManager=getSupportFragmentManager();        lifecycleFragment =(LifecycleFragment)fragmentManager.findFragmentById(R.id.Fragmentfragment);        button1.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                FragmentTransaction transaction = fragmentManager.beginTransaction();                transaction.remove(lifecycleFragment);                transaction.commit();            }        });        button2.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {            }        });    }}

这里写图片描述
在这儿我试着移除，但是无法移除。
“不可以的。要换Fragment只能通过框架布局来操作。关于灵活动态变化UI一般都使用Fragment的。如果你先remove掉，那就直接用框架布局来操作。”这是我百度到的一句话。

2、第二种（用框架布局）

第一个Fragment

public class FragmentOne extends Fragment {    private ImageView imageView;    @Nullable    @Override    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {        View view  = inflater.inflate(R.layout.layout_only_imageview,null);        imageView = (ImageView) view.findViewById(R.id.OnlyImageView);        imageView.setImageResource(R.mipmap.picture27);        return view;    }}

第二个Fragment

public class FragmentTwo extends Fragment{    private ListView mListView;    private List<String> mList;    @Nullable    @Override    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {        View view =inflater.inflate(R.layout.layout_only_listview,null);        mListView = (ListView) view.findViewById(R.id.OnlyListView);        mList =new ArrayList<>();        mList.add("你好");        mList.add("我好");        mList.add("大家好");        mList.add("你好");        mList.add("我好");        mList.add("大家好");        mList.add("你好");        mList.add("我好");        mList.add("大家好");        mList.add("你好");        mList.add("我好");        mList.add("大家好");        mList.add("你好");        mList.add("我好");        mList.add("大家好");        mList.add("你好");        mList.add("我好");        mList.add("大家好");        ArrayAdapter adapter =  new ArrayAdapter(getActivity(),android.R.layout.simple_expandable_list_item_1,mList);        mListView.setAdapter(adapter);        return view;    }}

再来看看activity的布局

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical"    tools:context=".studyfragment.fragment.FragmentActivityTest">    <FrameLayout        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:id="@+id/fragmentlayout"        android:layout_weight="1"        >    </FrameLayout>    <LinearLayout        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:orientation="horizontal"        android:id="@+id/FragmentLinearLayout"        >        <Button            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:text="上一页"            android:id="@+id/FragmentBtnUp"            android:layout_weight="1"            />        <Button            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:text="下一页"            android:id="@+id/FragmentBtnNext"            android:layout_weight="1"            />    </LinearLayout></LinearLayout>

这里只有一个FrameLayout和两个button
再来看看activity

public class FragmentActivityTest extends AppCompatActivity {    private Button button1,button2;    private FragmentManager manager;    private FragmentOne fragmentOne;    private FragmentTwo fragmentTwo;    private FrameLayout frameLayout;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_fragment_two);        manager = getSupportFragmentManager();        FragmentTransaction transaction = manager.beginTransaction();        fragmentTwo = new FragmentTwo();        fragmentOne = new FragmentOne();        transaction.add(R.id.fragmentlayout,fragmentTwo).commit();        button1= (Button) findViewById(R.id.FragmentBtnUp);        button2= (Button) findViewById(R.id.FragmentBtnNext);        button1.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                FragmentTransaction transaction = manager.beginTransaction();                //必须写在此处，因为它只执行一次就会销毁                transaction.replace(R.id.fragmentlayout,fragmentTwo);                transaction.commit();            }        });        button2.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                FragmentTransaction transaction = manager.beginTransaction();                //必须写在此处，因为它只执行一次就会销毁                transaction.replace(R.id.fragmentlayout,fragmentOne);                transaction.commit();            }        });    }}

这样就可以实现在FrameLayout中替换Fragment
看一下效果
这里写图片描述
还有一种是用transaction 的add、show、hide三个方法来显示。

3、第三种

用viewPager+Fragment组合来实现
先看几个类

public class FragmentPagerFour extends Fragment {    private ImageView imageView;    @Nullable    @Override    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {        View view  = inflater.inflate(R.layout.layout_only_imageview,null);        imageView = (ImageView) view.findViewById(R.id.OnlyImageView);        imageView.setImageResource(R.mipmap.a3);        return view;    }}

public class FragmentPagerOne extends Fragment {    private ImageView imageView;    @Nullable    @Override    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {        View view  = inflater.inflate(R.layout.layout_only_imageview,null);        imageView = (ImageView) view.findViewById(R.id.OnlyImageView);        imageView.setImageResource(R.mipmap.ic_launcher);        return view;    }}

public class FragmentPagerThree extends Fragment {    private ImageView imageView;    @Nullable    @Override    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {        View view  = inflater.inflate(R.layout.layout_only_imageview,null);        imageView = (ImageView) view.findViewById(R.id.OnlyImageView);        imageView.setImageResource(R.mipmap.a2);        return view;    }}

public class FragmentPagerTwo extends Fragment{    private ImageView imageView;    @Nullable    @Override    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {        View view  = inflater.inflate(R.layout.layout_only_imageview,null);        imageView = (ImageView) view.findViewById(R.id.OnlyImageView);        imageView.setImageResource(R.mipmap.a1);        return view;    }}

还有一个适配器：

public class TestFragmentPagerAdapter extends FragmentStatePagerAdapter {    private List<Fragment> list;    private Context intent;    public TestFragmentPagerAdapter(FragmentManager fm, List<Fragment> list, Context intent) {        super(fm);        this.list = list;        this.intent = intent;    }    @Override    public int getCount() {        return list.size();    }    @Override    public Fragment getItem(int position) {        return list.get(position);    }}

接下来是xml布局

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical">    <android.support.v4.view.ViewPager        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:id="@+id/ViewFragmentPagerTest"        android:layout_weight="1"        >    </android.support.v4.view.ViewPager>    <LinearLayout        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:orientation="horizontal"        android:id="@+id/FragmentPagerLinearLayout"        >        <ImageButton            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:id="@+id/FragmentPagerBtn1"            android:layout_weight="1"            />        <ImageButton            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:id="@+id/FragmentPagerBtn2"            android:layout_weight="1"            />        <ImageButton            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:id="@+id/FragmentPagerBtn3"            android:layout_weight="1"            />        <ImageButton            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:id="@+id/FragmentPagerBtn4"            android:layout_weight="1"            />    </LinearLayout></LinearLayout>

这里没有Fragment也没有FrameLayout，只有viewPager
接下来是activity

public class ActivityFragmentPager extends AppCompatActivity implements View.OnClickListener,ViewPager.OnPageChangeListener{    private ViewPager mViewPager;    private List<Fragment> list;    private ImageButton button1,button2,button3,button4;    private FragmentManager manager;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_fragment_pager);        mViewPager =(ViewPager)findViewById(R.id.ViewFragmentPagerTest);        list =  new ArrayList<>();        list.add(new FragmentPagerOne());        list.add(new FragmentPagerTwo());        list.add(new FragmentPagerThree());        list.add(new FragmentPagerFour());        manager = getSupportFragmentManager();        TestFragmentPagerAdapter testFragmentPagerAdapter =new TestFragmentPagerAdapter(manager,list,this);        mViewPager.setOnPageChangeListener(this);        mViewPager.setAdapter(testFragmentPagerAdapter);        init();    }    private void init() {        button1= (ImageButton) findViewById(R.id.FragmentPagerBtn1);        button1.setOnClickListener(this);        button2= (ImageButton) findViewById(R.id.FragmentPagerBtn2);        button2.setOnClickListener(this);        button3= (ImageButton) findViewById(R.id.FragmentPagerBtn3);        button3.setOnClickListener(this);        button4 = (ImageButton) findViewById(R.id.FragmentPagerBtn4);        button4.setOnClickListener(this);        button1.setImageResource(R.mipmap.a);        button2.setImageResource(R.mipmap.bb);        button3.setImageResource(R.mipmap.cc);        button4.setImageResource(R.mipmap.dd);    }    @Override    public void onClick(View v) {        switch (v.getId()){            case R.id.FragmentPagerBtn1:Fragment1();break;            case R.id.FragmentPagerBtn2:Fragment2();break;            case R.id.FragmentPagerBtn3:Fragment3();break;            case R.id.FragmentPagerBtn4:Fragment4();break;        }    }    private void Fragment1() {        mViewPager.setCurrentItem(0,true);    }    private void Fragment2() {        mViewPager.setCurrentItem(1,true);    }    private void Fragment3() {        mViewPager.setCurrentItem(2,true);    }    private void Fragment4() {        mViewPager.setCurrentItem(3,true);    }    @Override    public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {//        change(position);    }    @Override    public void onPageSelected(int position) {        change(position);    }    @Override    public void onPageScrollStateChanged(int state) {//        change(state);    }    private void change(int pp){        Toast.makeText(this,"ssdfsdf",Toast.LENGTH_SHORT).show();        button1.setImageResource(R.mipmap.aa);        button2.setImageResource(R.mipmap.bb);        button3.setImageResource(R.mipmap.cc);        button4.setImageResource(R.mipmap.dd);        switch (pp){            case 0: button1.setImageResource(R.mipmap.a);break;            case 1:button2.setImageResource(R.mipmap.b);break;            case 2:button3.setImageResource(R.mipmap.c);;break;            case 3:button4.setImageResource(R.mipmap.d);;break;        }    }}

我们看一下效果
这里写图片描述
这样就很容易地实现了Fragment的替换。

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