android开发教程系列(1)Activity

Android中生命周期的知识
注意：如果要在android机制中打印出System.out的输出语句
需要配置过滤器，名称为System.out就行

1.Activity的生命周期函数

public class Activity extends ApplicationContext {
/**Activity1第一次被创建时*/
protected void onCreate(Bundle savedInstanceState);
/**当Activity1被看到时调用*/
protected void onStart();
/**当从Activity2返回时调用*/
protected void onRestart();
/**当Activity1被操作时调用*/
protected void onResume();
/**启动跳转到Activity2时调用*/
protected void onPause();
/**Activity1处于不可见的状态时调用*/
protected void onStop();
/**此时销毁的是Activity2*/
调用finish()方法或者系统资源不够用时调用
protected void onDestroy();
}
2.Task基本概念
任务：一个存放Activity的栈
注：点击Back按钮，将当前的Activity弹出栈
启动Intent后使用finish方法，就将Activity销毁了
配置一个以对话框形式的Activity：
<activity android:name=".ThirdActivity"
android:label="@string/thirdName"
android:theme="@android:style/Theme.Dialog">
</activity>
此时之前的Activity没有被完全覆盖，所以不调用onStop()
代码实现：

FirstActivity.java

package com.apkway;
import com.apkway.R;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
/**
* @author ghost
* 第一个Activity
*/
public class FirstActivity extends Activity {
private Button start1;
private Button start2;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
this.setContentView(R.layout.first);
System.out.println("1Activity!onCreate");
start1 = (Button)this.findViewById(R.id.start1);
start2 = (Button)this.findViewById(R.id.start2);
OnClickListener listener1 = new OnClickListener() {
@Override
public void onClick(View v) {
Intent it = new Intent(FirstActivity.this,SecondActivity.class);
startActivity(it);
}
};
start1.setOnClickListener(listener1);

OnClickListener listener2 = new OnClickListener() {

@Override
public void onClick(View v) {
Intent it = new Intent(FirstActivity.this,ThirdActivity.class);
startActivity(it);
}
};
start2.setOnClickListener(listener2);
}

@Override
protected void onStart() {
// TODO Auto-generated method stub
super.onStart();
System.out.println("1Activity!onStart");
}

@Override
protected void onStop() {
// TODO Auto-generated method stub
super.onStop();
System.out.println("1Activity!onStop");
}

@Override
protected void onRestart() {
// TODO Auto-generated method stub
super.onRestart();
System.out.println("1Activity!onRestart");
}

@Override
protected void onResume() {
// TODO Auto-generated method stub
super.onResume();
System.out.println("1Activity!onResume");
}

@Override
protected void onPause() {
// TODO Auto-generated method stub
super.onPause();
System.out.println("1Activity!onPause");
}

@Override
protected void onDestroy() {
// TODO Auto-generated method stub
super.onDestroy();
System.out.println("1Activity!onDestroy");
}
}

SecondActivity.java

package com.apkway;
import com.apkway.R;
import android.app.Activity;
import android.os.Bundle;
/**
* @author ghost
* 第二个Activity
*/
public class SecondActivity extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.second);
System.out.println("2Activity!onCreate");
}

@Override
protected void onStart() {
// TODO Auto-generated method stub
super.onStart();
System.out.println("2Activity!onStart");
}

@Override
protected void onStop() {
// TODO Auto-generated method stub
super.onStop();
System.out.println("2Activity!onStop");
}

@Override
protected void onRestart() {
// TODO Auto-generated method stub
super.onRestart();
System.out.println("2Activity!onRestart");
}

@Override
protected void onResume() {
// TODO Auto-generated method stub
super.onResume();
System.out.println("2Activity!onResume");
}

@Override
protected void onPause() {
// TODO Auto-generated method stub
super.onPause();
System.out.println("2Activity!onPause");
}

@Override
protected void onDestroy() {
// TODO Auto-generated method stub
super.onDestroy();
System.out.println("2Activity!onDestroy");
}
}

ThirdActivity.java

package com.apkway;
import android.app.Activity;
import android.os.Bundle;
/**
* @author ghost
* 第三个Activity
*/
public class ThirdActivity extends Activity{

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
this.setContentView(R.layout.third);
}
}
xml的配置很简单，相信对android入门的同学们肯定是不在话下的，好的，这讲就到这里了，源码也附上了，有什么问题留言交流！

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