Android菜鸟基础笔记
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Android菜鸟基础笔记
按钮路径设置
setContentView(R.layout.two); findViewById(R.id.button2).setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { startActivity(new Intent(MainActivity.this, Main2Activity.class)); } }); findViewById(R.id.button3).setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { startActivity(new Intent(Intent.ACTION_VIEW, Uri.parse("https://www.baidu.com/"))); } });
创建文本
<TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Hello World!" android:id="@+id/tv"/>
数据传递
(1)传递简单数据
Main:
findViewById(R.id.btnStartAty).setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { Intent i=new Intent(MainActivity.this,TheAty.class); i.putExtra("data","123456"); startActivity(i); } });
Activity:
public class TheAty extends AppCompatActivity { private TextView tv; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_the_aty); Intent i=getIntent(); tv=(TextView)findViewById(R.id.tv); tv.setText(i.getStringExtra("data")); }}
(2)传递数据包Bundle
Main:
findViewById(R.id.btnStartAty).setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { Intent i=new Intent(MainActivity.this,TheAty.class); Bundle b=new Bundle(); b.putString("name","ccy"); b.putInt("age",20); i.putExtras(b); startActivity(i); } });
Activity:
public class TheAty extends AppCompatActivity { private TextView tv; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_the_aty); Intent i=getIntent(); Bundle data=i.getExtras(); tv=(TextView)findViewById(R.id.tv); tv.setText(String.format("name=%s,age=%d,buchunzai=%s",data.getString("name"),data.getInt("age"),data.getString("name1","X"))); }}
显示提示框(会自动消失)
(1)下方
Toast.makeText(this, "Toast text, normal", Toast.LENGTH_SHORT).show(); Toast t2=Toast.makeText(this, "Toast text with specific position", Toast.LENGTH_LONG); t2.setGravity(Gravity.CENTER_HORIZONTAL|Gravity.BOTTOM, 0, 10); //设置文本的位置,使文本显示靠下一些 t2.show();
(2)上方
Toast t3=Toast.makeText(this, "Toast text with specific margin and position", Toast.LENGTH_SHORT); t3.setGravity(Gravity.CENTER_HORIZONTAL|Gravity.BOTTOM, 0, 0); t3.setMargin(0f, 0.5f); t3.show();
使用Service
(1)新建Service
(2) main.xml(垂直排列android:orientation=”vertical”)
<Button android:text="启动服务" android:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@+id/btnStartService" tools:layout_editor_absoluteX="0dp" tools:layout_editor_absoluteY="76dp" /> <Button android:text="停止服务" android:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@+id/btnStopService" tools:layout_editor_absoluteX="0dp" tools:layout_editor_absoluteY="0dp" />
(3)main.java
private Intent intent; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); intent=new Intent(MainActivity.this,MyService.class); findViewById(R.id.btnStartService).setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) {//(可与下面那句取代) startService(new Intent(MainActivity.this,MyService.class)); startService(intent); } }); findViewById(R.id.btnStopService).setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) {//(可与下面那句取代) stopService(new Intent(MainActivity.this,MyService.class)); stopService(intent); } }); }
广播接收器 BroadcastReceiver
新建:new->Other->BroadcastReceiver
(1)运用BroadcastReceiver传递数据并显示
BroadcastReceiver.java: public class MyReceiver extends BroadcastReceiver { public MyReceiver() { } @Override public void onReceive(Context context, Intent intent) { System.out.println("接受到了消息,消息的内容是:"+intent.getStringExtra("data")); }}
MainAtivity.java:
protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); findViewById(R.id.btnSendMsg).setOnClickListener(this);/*事件监听器*/ } @Override public void onClick(View v) { switch (v.getId()){ case R.id.btnSendMsg: Intent i=new Intent(this,MyReceiver.class); i.putExtra("data","jkxy");/*传递数据*/ sendBroadcast(i); break; } }
activity_main.xml:
<Button android:text="发送消息" android:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@+id/btnSendMsg" />
BroadcastReceiver的注册注销
(1)AndroidManifest.xml:删除receiver模块
(2)MyReceiver.java:
package com.example.a83541.learnbroadcastreceiver;import android.content.BroadcastReceiver;import android.content.Context;import android.content.Intent;public class MyReceiver extends BroadcastReceiver { public static final String ACTION="com.example.a83541.learnbroadcastreceiver.intent.action.Myreceiver";/*重点*/ public MyReceiver() { } @Override public void onReceive(Context context, Intent intent) { System.out.println("接受到了消息,消息的内容是:"+intent.getStringExtra("data")); }}
(3)MainAtivity.java:
/*事件监听器*/ findViewById(R.id.btnSendMsg).setOnClickListener(this); findViewById(R.id.btnReg).setOnClickListener(this); findViewById(R.id.btnUnreg).setOnClickListener(this);/*注册注销*/public void onClick(View v) { switch (v.getId()){ case R.id.btnSendMsg: Intent i=new Intent(MyReceiver.ACTION); i.putExtra("data","jkxy"); sendBroadcast(i); break; case R.id.btnReg: if(receiver==null){ receiver=new MyReceiver(); registerReceiver(receiver,new IntentFilter(MyReceiver.ACTION)); } break; case R.id.btnUnreg: if(receiver!=null){ unregisterReceiver(receiver); receiver=null; } break; } } //防止重复注册多个receiver private MyReceiver receiver=null;
广播接收器 BroadcastReceiver优先级问题
(1)新建一个MyReceive1
(2)内容可修改,其他跟上面一样
(3)AndroidManifest.xml:
1.默认情况,从上到下执行
<receiver android:name=".MyReceiver1" android:enabled="true" android:exported="true"> <intent-filter> <action android:name="com.example.a83541.learnbroadcastreceiver.intent.action.Myreceiver"/> </intent-filter> </receiver> <receiver android:name=".MyReceiver"> <intent-filter> <action android:name="com.example.a83541.learnbroadcastreceiver.intent.action.Myreceiver"/> </intent-filter> </receiver>
2.按android:priority大小执行,大的先执行
<receiver android:name=".MyReceiver1" android:enabled="true" android:exported="true"> <intent-filter android:priority="10"> <action android:name="com.example.a83541.learnbroadcastreceiver.intent.action.Myreceiver"/> </intent-filter> </receiver> <receiver android:name=".MyReceiver"> <intent-filter android:priority="11"> <action android:name="com.example.a83541.learnbroadcastreceiver.intent.action.Myreceiver"/> </intent-filter> </receiver>
请求权限实例
(1)activity_main.xml中创建WebView(等于号后面的值可随意设置)
<WebView android:layout_width="match_parent" android:layout_height="20pt" android:id="@+id/wv" android:layout_weight="0.96"> </WebView>
(2)MainActivity.java:
public class MainActivity extends AppCompatActivity { private WebView wv; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); wv= (WebView) findViewById(R.id.wv); wv.loadUrl("http://www.qq.com"); }}
(3)重点,设置权限,访问网络
例:
<?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.example.a83541.learnbroadcastreceiver"> <uses-permission android:name="android.permission.INTERNET"/> /*插入位置*/ <application android:allowBackup="true" android:icon="@mipmap/ic_launcher" android:label="@string/app_name" android:supportsRtl="true" android:theme="@style/AppTheme"> <activity android:name=".MainActivity"> <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> </application> </manifest>
为代码添加权限检查
(1)新建class,eg:Hello.class:
public class Hello { public static final String PERMISSION_SAY_HELLO="com.example.a83541.learnbroadcastreceiver"; public static void sayHello(Context context) /*注意传入参数类型*/ { int checkResult =context.checkCallingOrSelfPermission(PERMISSION_SAY_HELLO);/*判断是否有权限*/ if(checkResult!= PackageManager.PERMISSION_GRANTED)/*如果没有权限,弹出错误警告*/ { throw new SecurityException("执行sayhello方法需要com.example.a83541.learnbroadcastreceiver权限"); } System.out.println("Hello ccy");/*有权限可以执行的语句*/ }}
(2)AndroidManifest.xml:
<permission android:name="com.example.a83541.learnbroadcastreceiver"/>/*声明需要此权限*/ <uses-permission android:name="com.example.a83541.learnbroadcastreceiver"/>/*使用此权限,如没有此语句则无法运行*/
(3)MainActiity.java:
public class MainActivity extends AppCompatActivity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); Hello.sayHello(this);/*运行Hello.java中的sayHello方法*/ }}
为基本组件添加权限检查(以Activity为例),同一个应用跳转不需要权限
(1)新建Activity,eg:MyAty,在MyAty.xml中添加内容
(2)新建app,File->New->New Module,eg:anotherapp
(3)app/AndroidManifest.xml:
<permission android:name="com.example.a83541.myapplication.permission.MyAty"/>/*声明所需权限*/
(4)app/AndroidManifest.xml:
findViewById(R.id.btnStartMyAty).setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { startActivity(new Intent("com.example.a83541.myapplication.intent.action.MyAty"));/*利用action打开MyAty*/ } });
(6)app/MainActivity可不管:在MainAtivity中创建一个按钮,id为btnStartMyAty,可用于证明同一个应用不需要访问权限。
protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); findViewById(R.id.btnStartMyAty).setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { startActivity(new Intent(MainActivity.this,MyAty.class)); } }); }
(7)antherapp/Manifest.xml中声明权限
<uses-permission android:name="com.example.a83541.myapplication.permission.MyAty"/>
(8)启动app和antherapp
Fragment
显示Fragment时(跟用户交互)要调用的核心的生命周期方法如下:
1. 把Fragment对象跟Activity关联时,调用onAttach(Activity)方法;
2. Fragment对象的初始创建时,调用onCreate(Bundle)方法;
3. onCreateView(LayoutInflater, ViewGroup, Bundle)方法用于创建和返回跟Fragment关联的View对象;
4. onActivityCreate(Bundle)方法会告诉Fragment对象,它所依附的Activity对象已经完成了Activity.onCreate()方法的执行;
5. onStart()方法会让Fragment对象显示给用户(在包含该Fragment对象的Activity被启动后);
6. onResume()会让Fragment对象跟用户交互(在包含该Fragment对象的Activity被启恢复后)。
Fragment对象不再使用时,要反向回调的方法:
1. 因为Fragment对象所依附的Activity对象被挂起,或者在Activity中正在执行一个修改Fragment对象的操作,而导致Fragment对象不再跟用户交互时,系统会调用Fragment对象的onPause()方法;
2. 因为Fragment对象所依附的Activity对象被终止,或者再Activity中正在执行一个修改Fragment对象的操作,而导致Fragment对象不再显示给用户时,系统会调用Fragment对象的onStop()方法。
3. onDestroyView()方法用于清除跟Fragment中的View对象关联的资源;
4. Fragment对象的状态被最终清理完成之后,要调用onDestroy()方法;
5. 在Fragment对象不再跟它依附的Activity关联的时候,onDetach()方法会立即被调用
Spinner
activity_main.xml:
<Spinner android:layout_width="match_parent" android:layout_height="wrap_content" android:id="@+id/spinner" />
MainActivity.java:
private Spinner s; private String[] dataSource=new String[]{"1","2","3"};/*菜单选项*/ @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); s= (Spinner) findViewById(R.id.spinner); s.setAdapter(new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1,dataSource)); s.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() { @Override public void onItemSelected(AdapterView<?> parent, View view, int position, long id) { System.out.println("X"+dataSource[position]); } @Override public void onNothingSelected(AdapterView<?> parent) { } }); }
android TextView控件如何显示数组内容
通过数组循环显示到TextView上。
1、获取数组
2、获取TextView组件
3、循环拼接数组成字符串,显示到TextView中
示例:
TextView tv = (TextView)findViewById(R.id.xxxx);//获取一个TextViewString ct = "";//定义一个字符串for(int i=0;i<arr.length;i++){ ct = ct + arr[i];//数组拼接成字符串}tv.setText(ct);//在TextView中显示数组内容。
Error:Gradle version 2.2 is required
1、修改项目中gradle/warpper/gradle-warpper.properties文件中的distributionUrl路劲。如下:
distributionUrl=https://services.gradle.org/distributions/gradle-2.2-all.zip 改: //你本机AS中gradle的版本 distributionUrl=https://services.gradle.org/distributions/gradle-2.10-all.zip
2、修改build.gradle文件中的classpath
uildscript { … dependencies { classpath ‘com.android.tools.build:gradle:1.2.3’ } 改: //你本机的AS的gradle的版本 uildscript { … dependencies { classpath ‘com.android.tools.build:gradle:2.1.0’ }
颜色和不透明度 (alpha) 值以十六进制表示法表示。任何一种颜色的值范围都是 0 到 255(00 到 ff)。对于 alpha,00 表示完全透明,ff 表示完全不透明。表达式顺序是“aabbggrr”,其中“aa=alpha”(00 到 ff);“bb=blue”(00 到 ff);“gg=green”(00 到 ff);“rr=red”(00 到 ff)。例如,如果您希望对某叠加层应用不透明度为 50% 的蓝色,则应指定以下值:7fff0000
设置背景图片透明度(超简单)
Java代码
View v = findViewById(R.id.content);//找到你要设透明背景的layout 的id v.getBackground().setAlpha(100);//0~255透明度值button透明:android:background="#00000000"
java截取字符串,截串,substring和split,分割字母和数字,正则缝隙
关键字: java截取字符串 截串 substring
需求,把”01:大汽车”,分成01和大汽车
有两种做法:一是substring
Java代码
package test; public class substringTest { public static void main(String args[]) { String N = "01:大汽车"; String L=""; String R=""; int k= N.length(); for (int i = 0; i < N.length(); i++) { if (N.substring(i, i + 1).equals("|")) { L=N.substring(0,i).trim(); R=N.substring(i+1,k).trim(); } else { } System.out.println(L); System.out.println(R); } } }
或
public class splitTest { public static void main(String[] args) { String s = new String("01:大汽车"); String a[] = s.split(":"); System.out.println(a[0]); System.out.println(a[1]); } }
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