Android之Activity的生命周期和Activity间的跳转和数据传递

           Activity，是Android中一个重要的组件。就像任务管理进程，每个Activity负责一个任务，一般都是一个页面对应一个Activity，Activity负责响应当前页面的所有请求和处理。而Activity的生命周期，也和进程很类似，它有创建（OnCreate）、开始（onStart）、暂停（onPause）、唤醒（onResume）、停止（onStop）、重启（onRestart）、销毁（onDestroy）等状态。下面一幅图，清楚地描述了这些状态的转变：

        


           Activity启动的流程包括：onCreate()->onStart()->onResume()

           Activity关闭的流程包括：onPause()->onStop()->onDestroy()。

           Activity重启的流程包括：onPause()->onResume()或者onStop()->onRestart()

           下面再通过实例来讲述Activity的生命周期：

           （1）启动Activity1

          


           （2）从Activity1中启动Activity2（注意Activity1这里并没有调用finish()方法）

           


           （3）从Activity2中返回Activity1（注意Activity2这里调用了finish()方法，会引发onDestroy()方法）

           


           （4）退出Activity1，程序结束

          


           可以看出Activity1经历的生命周期为：onCreate()->onStart()->onResume()->onPause()->onStop()->onRestart()->onResume()->onPause()->onStop()->onDestroy()

           Activity2经历的生命周期为：onCreate()->onStart()->onResume()->onPause()->onStop()->onDestroy()

           实例视图与具体代码如下：

          

    


          

      


           1、布局文件

           Activity1的布局文件main.xml：

          

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<LinearLayout
android:orientation="horizontal"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
>
<TextView
android:id="@+id/textView01"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="输入字符串："/>
<EditText
android:id="@+id/et_string"
android:layout_width="203px"
android:layout_height="47px"
android:textSize="18sp"/>
</LinearLayout>
<Button
android:id="@+id/bt_toActivity2"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="计算字符串长度"/>
<LinearLayout
android:orientation="horizontal"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
>
<TextView
android:id="@+id/textView02"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="字符串长度为： "/>
<TextView
android:id="@+id/tv_result"
android:layout_width="202px"
android:layout_height="wrap_content"
android:textSize="18sp"/>
</LinearLayout>
<Button
android:id="@+id/bt_url"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="打开百度网站"/>

</LinearLayout>

           Activity2的布局文件 mylayout.xml：

           

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<!-- 显示结果 -->
<TextView
android:id="@+id/tv_showResult"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text=""
/>
<!-- 返回另一个Activity -->
<Button
android:id="@+id/bt_back"
android:layout_width="100px"
android:layout_height="wrap_content"
android:text="返回"
/>
</LinearLayout>

           2、代码

           Activity1的程序代码

          

package com.myandroid.test;

import android.app.Activity;
import android.content.Intent;
import android.content.SharedPreferences;
import android.net.Uri;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class ActivityIntent extends Activity {
private Button bt_toActivity;
private Button bt_outsideIntent;
private EditText et_string;
private TextView tv_result;

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Log.e("Lifecycle_Activity1", "onCreate()");

et_string = (EditText) findViewById(R.id.et_string);
bt_toActivity = (Button) findViewById(R.id.bt_toActivity2);
bt_outsideIntent = (Button) findViewById(R.id.bt_url);
tv_result = (TextView) findViewById(R.id.tv_result);
bt_toActivity.setOnClickListener(new ClickEvent());
bt_outsideIntent.setOnClickListener(new ClickEvent());
}

//销毁：onPause()->onStop()->onDestroy()
@Override
protected void onDestroy() {
super.onDestroy();
Log.e("Lifecycle_Activity1", "onDestroy()");
}

//暂停：onStart()->onPause()
@Override
protected void onPause() {
super.onPause();
Log.e("Lifecycle_Activity1", "onPause()");

//把数据保存到类似于Session之类的存储集合里面
SharedPreferences.Editor saveData = getPreferences(0).edit();
saveData.putString("value", et_string.getText().toString());
saveData.commit();
}

//重启：onPause()->onResume()
@Override
protected void onResume() {
super.onResume();
Log.e("Lifecycle_Activity1", "onResume()");

//从共享数据存储对象中获取所需的数据
SharedPreferences getData = getPreferences(0);
String value = getData.getString("value", null);
if(value != null) {
et_string.setText(value);
}
}

//开始：onCreate()->onStart()
@Override
protected void onStart() {
super.onStart();
Log.e("Lifecycle_Activity1", "onStart()");
}

//停止:onPause()->onStop()
@Override
protected void onStop() {
super.onStop();
Log.e("Lifecycle_Activity1", "onStop()");
}

//重启：onStop()->reonRestart()
@Override
protected void onRestart() {
super.onRestart();
Log.e("Lifecycle_Activity1", "onRestart()");
}

/**
* 处理上一个Activity的返回结果
*/
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
// TODO Auto-generated method stub
super.onActivityResult(requestCode, resultCode, data);
switch(resultCode) {

case RESULT_OK:	//执行成功，返回
Bundle bundle = data.getExtras(); 		//获取intent里面的bundle对象
int length = bundle.getInt("result");
tv_result.setText("" + length);
break;

default:
break;
}
}

//重写点击监听器类
class ClickEvent implements OnClickListener {

@Override
public void onClick(View v) {
// TODO Auto-generated method stub

switch(v.getId()) {

case R.id.bt_toActivity2:	//跳转到另一个Activity
Intent intent = new Intent();
intent = intent.setClass(ActivityIntent.this, AnotherActivity.class);
Bundle bundle = new Bundle();
bundle.putString("string", et_string.getText().toString());
intent.putExtras(bundle);
startActivityForResult(intent,0);	//采用Activity间信息交流启动方式，
//比如A启动B，B结束后，返回到A的同时会执行	onActivityResult()方法
//处理上一个Activity即B传递的结果集。
//ActivityIntent.this.finish();	//会触发onDestroy();
break;

case R.id.bt_url:	//Intent还可以调用外部组件，但有些组件会有权限控制
Uri uri = Uri.parse("http://www.baidu.com");
Intent outerIntent = new Intent(Intent.ACTION_VIEW, uri);
startActivity(outerIntent);
break;
default:
break;
}
}

}
}

           Activity2的程序代码

           

package com.myandroid.test;

import java.text.DecimalFormat;
import java.text.NumberFormat;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;

public class AnotherActivity extends Activity {
private String string;

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.mylayout);
Log.e("Lifecycle_Activity1", "onCreate()");

Intent intent = this.getIntent();	 	//获取intent对象
Bundle bundle = intent.getExtras(); 	//获取intent里面的bundle对象
string = bundle.getString("string"); 	//获取字符串
((TextView)findViewById(R.id.tv_showResult)).setText(
"字符串 " + string +" 长度为: " + string.length());
Button bt_back = (Button) findViewById(R.id.bt_back);
bt_back.setOnClickListener(new ClickEvent());

}

@Override
protected void onDestroy() {	//销毁：onPause()->onStop()->onDestroy()
// TODO Auto-generated method stub
super.onDestroy();
Log.e("Lifecycle_Activity2", "onDestroy()");
}

@Override
protected void onPause() {		//暂停：onStart()->onPause()
// TODO Auto-generated method stub
super.onPause();
Log.e("Lifecycle_Activity2", "onPause()");
}

@Override
protected void onResume() {		//重启：onPause()->onResume()
// TODO Auto-generated method stub
super.onResume();
Log.e("Lifecycle_Activity2", "onResume()");
}

@Override
protected void onStart() {		//开始：onCreate()->onStart()
// TODO Auto-generated method stub
super.onStart();
Log.e("Lifecycle_Activity2", "onStart()");
}

@Override
protected void onStop() {		//停止:onPause()->onStop()
// TODO Auto-generated method stub
super.onStop();
Log.e("Lifecycle_Activity2", "onStop()");
}

@Override
protected void onRestart() {		//重启
// TODO Auto-generated method stub
super.onRestart();
Log.e("Lifecycle_Activity2", "onRestart()");
}

class ClickEvent implements OnClickListener {

@Override
public void onClick(View v) {
// TODO Auto-generated method stub

switch(v.getId()) {
case R.id.bt_back:
Intent intent = new Intent();
intent = intent.setClass(AnotherActivity.this, ActivityIntent.class);
Bundle bundle = new Bundle();
bundle.putInt("result", string.length());
intent.putExtras(bundle);

//返回刚刚创建的intent给上一个Activity，并且关闭当前Activity
AnotherActivity.this.setResult(RESULT_OK, intent);
AnotherActivity.this.finish();	//会触发onDestroy();
break;
default:
break;
}
}

}
}

 

           最后记得在AndroidManifest.xml添加Activity2的信息，如下：

          

<application android:icon="@drawable/icon" android:label="@string/app_name">
............
<activity android:name="AnotherActivity"></activity>
</application>

          下一篇补充下Activity之间的跳转和传值，以及从如何获取上一个Activity返回的结果和数据状态保存等内容。简单的说，Intent、Bundle、SharedPreferences等应用。