Android——通过案例代码测试Activity的整个生命周期

在Activity创建、可视、隐藏、重新可视、销毁等过程中，我们有时候需要做一些特殊处理，到底应该在Activity的哪个函数中进行处理操作呢？这就是今天我要讲的。

一、案例代码

1、MainActivity.java
这个Activity是项目的启动Activity，也就是主Activity。通过这个Activity启动其他Activity，但是主Activity只能暂时不可见，不能销毁，否则，其他Activity就无法再返回到这个主Activity了。直接上代码：

package com.ju.testphpserver.activity;import com.ju.testphpserver.model.UserInfoModel;import com.ju.testphpserver.object.User;import com.ju.testphpserver.R;import android.app.Activity;import android.app.AlertDialog;import android.content.DialogInterface;import android.content.Intent;import android.os.Bundle;import android.os.Handler;import android.os.Message;import android.util.Log;import android.view.Menu;import android.view.MenuItem;import android.view.View;import android.view.View.OnClickListener;import android.view.Window;import android.widget.Button;import android.widget.EditText;import android.widget.TextView;public class MainActivity extends Activity {    private TextView userIDTV;    private TextView userNameTV;    private TextView passwordTV;    private Button getBtn;    private Button deleteBtn;    private Button updateBtn;    private EditText userIDET;    private Intent intent;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        requestWindowFeature(Window.FEATURE_NO_TITLE);        setContentView(R.layout.activity_main);        deleteBtn = (Button) findViewById(R.id.deleteBtn);        intent = this.getIntent();        getBtn.setOnClickListener(new OnClickListener() {            @Override            public void onClick(View v) {                initActivity();            }        });        deleteBtn.setOnClickListener(new OnClickListener() {            @Override            public void onClick(View v) {                Intent intent = new Intent(MainActivity.this, DeleteActivity.class);                startActivity(intent);            }        });        Log.i("ju", "MainActivity:onCreate()");    }    @Override    public void onStart(){        super.onStart();        Log.i("ju", "MainActivity:onStart()");    }    @Override    public void onResume(){        super.onResume();        Log.i("ju", "MainActivity:onResume()");    }    @Override     public void onPause(){        super.onPause();        Log.i("ju", "MainActivity:onPause()");    }    @Override    protected void onStop() {          super.onStop();          Log.i("ju", "MainActivity:onStop()");    }       @Override     public void onDestroy(){        super.onDestroy();        Log.i("ju", "MainActivity:onDestroy()");    }}

2、DeleteActivity.java

package com.ju.testphpserver.activity;import com.ju.testphpserver.model.UserInfoModel;import com.ju.testphpserver.R;import android.app.Activity;import android.app.AlertDialog;import android.content.DialogInterface;import android.content.Intent;import android.os.Bundle;import android.os.Handler;import android.util.Log;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;import android.widget.EditText;public class DeleteActivity extends Activity {    private Button gobackBtn;    private Button deleteUserBtn;    private EditText userIDTV;    private Intent intent;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_deletectivity);        gobackBtn = (Button) findViewById(R.id.gobackBtn);        deleteUserBtn = (Button) findViewById(R.id.deleteUserBtn);        intent = this.getIntent();        gobackBtn.setOnClickListener(new OnClickListener() {            @Override            public void onClick(View v) {                DeleteActivity.this.setResult(RESULT_OK, intent);                DeleteActivity.this.finish();            }        });        Log.i("ju", "DeleteActivity:onCreate()");    }    @Override    public void onStart(){        super.onStart();        Log.i("ju", "DeleteActivity:onStart()");    }    @Override    public void onResume(){        super.onResume();        Log.i("ju", "DeleteActivity:onResume()");    }    @Override     public void onPause(){        super.onPause();        Log.i("ju", "DeleteActivity:onPause()");    }    @Override    protected void onStop() {          super.onStop();          Log.i("ju", "DeleteActivity:onStop()");    }       @Override     public void onDestroy(){        super.onDestroy();        Log.i("ju", "DeleteActivity:onDestroy()");    }}

3、运行截图：

二、各类情景分析

1、当项目启动时，依次启动函数的顺序是：
MainAcitivity:onCreate()
->
MainAcitivity:onStart()
->
MainActivity:onResume()

2、当点击“删除页面”时，视图切换到了删除页面：DeleteActivity，依次启动函数的顺序是：
MainActivity:onPause()
->
DeleteActivity:onCreate()
->
DeleteActivity:onStart()
->
DeleteActivity:onResume()
->
MainActivity:onStop()

3、当点击删除页面的“返回”按钮时，视图再次切换回主Activity：MainActivity，依次启动函数顺序是：
DeleteActivity:onPause()
->
MainActivity:onStart()
->
MainActivity:onResume()
->
DeleteAcvitiy:onStop()
->
DeleteActivity:OnDestroy()

4、当项目正在运行，遇到锁屏时：
MainActivity:onPause()
->
MainActiviy:onStop()

屏幕解锁后，重新唤醒应用，执行以下顺序：
MainActivity:onStart()
->
MainActivity:onResume()

5、当直接退出application时，执行以下顺序：
MainActivity:onPause()
->
MainActiviy:onStop()
->
MainActivity：onDestroy()

三、应用

如果我们在开发过程中，需要对某个activity的某个过程进行处理，就可以将代码直接写在相应的函数中。
例如：
1、初始化代码，只执行一次，一般写在onCreate()函数中。
2、内存回收类代码，一般写在onDestroy()函数中。
3、某个视图每次重新加载时，需要更新的代码，一般写在onStart()函数中。

以上只是我个人意见，希望对各位写代码有一定的帮助吧。

参考文章（activity）：
http://www.runoob.com/android/android-acitivities.html