<?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">
	<Button android:id="@+id/c19_pick"
	  android:layout_width="fill_parent"
	  android:layout_height="fill_parent"
	  android:layout_weight="1"
	  android:text="Pick"
	  android:enabled="true" />
	<Button android:id="@+id/c19_view"
	  android:layout_width="fill_parent"
	  android:layout_height="fill_parent"
	  android:layout_weight="1"
	  android:text="View"
	  android:enabled="false" />  
</LinearLayout>

public class Chapter19Test1 extends Activity{
    private int testNum = 0; //实验：跟踪testNum
    
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.chapter_19_test1);
		
		Button pickButton = (Button)findViewById(R.id.c19_pick);
		pickButton.setText("Pick : " + testNum);
		
		pickButton.setOnClickListener(new View.OnClickListener() {
			/*每按pick按键一次，计数器testNum就加一*/
			public void onClick(View v) {
				testNum ++;
				System.out.println("Pick : " + testNum);
				((Button)v).setText("Pick : " + testNum);
			}
		});
		
		viewButton.setEnabled(contact != null);
	}

｝ 

protected void onCreate(Bundle savedInstanceState) {
         ... ...		
	Button pickButton = (Button)findViewById(R.id.c19_pick);
	/*从Bundle中获取保存的数据，进行恢复*/
	if(savedInstanceState != null){
		testNum = savedInstanceState.getInt("count");
	}
	pickButton.setText("Pick : " + testNum);
	
	pickButton.setOnClickListener(new View.OnClickListener() {
	      ......
	});
}
 
@Override
/*通过onSaveInstanceState()来进行数据保存，存放如Bundle中。*/
protected void onSaveInstanceState(Bundle outState) {
	// TODO Auto-generated method stub
	super.onSaveInstanceState(outState);
	outState.putInt("count", testNum);
} 

public class Chapter19Test1 extends Activity{
	static final int PICK_REQUEST=1000;
	
	private Button viewButton = null;
	private Uri contact = null;
	  
	protected void onCreate(Bundle savedInstanceState) {
		... ... 		
		pickButton.setOnClickListener(new View.OnClickListener() {
			/* 下面给1）如何调用contact列表；2）如何调用代返回值的intent */		
			public void onClick(View v) {
				Intent intent = new Intent(Intent.ACTION_PICK, ContactsContract.Contacts.CONTENT_URI);
				startActivityForResult(intent, PICK_REQUEST);
			}
		});
		
		viewButton.setOnClickListener(new View.OnClickListener() {
			/* 1）如何调用显示某个contact的详细内容*/
			public void onClick(View v) {
				startActivity(new Intent(Intent.ACTION_VIEW,contact));
			}
		});

		restoreMe(savedInstanceState); 
		viewButton.setEnabled(contact != null);
	}	

	@Override
	/* 2）如何获取intent的返回数值，通过requestCode的匹配，确定是否我们所需*/
	protected void onActivityResult(int requestCode, int resultCode, Intent data) {
		super.onActivityResult(requestCode, resultCode, data);		
		if(requestCode == PICK_REQUEST){
			if(resultCode == RESULT_OK){
				contact = data.getData();
				viewButton.setEnabled(true);
			}
		}
	}

	@Override
	/* 3）用于屏幕旋转等情况的数据保存，这是系统自动调用的。*/
	protected void onSaveInstanceState(Bundle outState) {
		super.onSaveInstanceState(outState);
		if(contact != null){
			outState.putString("contact", contact.toString());
		}
	}

	/* 3）在onCreate中调用，用与屏幕旋转时，恢复数据，其实还包括了其他的情况，例如电池电能太低*/
	private void restoreMe(Bundle  state){
		contact = null;
		if(state != null){
			String contactUri = state.getString("contact");
			if(contactUri != null){
				contact = Uri.parse(contactUri);
			}
		}
	}

} 

public class Chapter19Test2 extends Activity{
	... ... 
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		... ...
		/* 恢复数据 */
		restoreMe(); 
		... ... 
	}
	
	... ...
	
	@Override
	/*通过onRetainNonConfigurationInstance()直接保存object,在之前的例子是保存了Uri的toString()信息*/
	public Object onRetainNonConfigurationInstance() {
		return contact;
	}

	/* 恢复数据，直接获得对象*/
	private void restoreMe(){
		contact = null;
		if(getLastNonConfigurationInstance()!= null){
			contact = (Uri)getLastNonConfigurationInstance();
		}
	}
} 

public class Chapter19Test3 extends Activity{
	private Button pickButton = null;
	private int count = 0;
        
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setupViews();
	}

	private void setupViews(){
		setContentView(R.layout.chapter_19_test1);
		
		pickButton = (Button)findViewById(R.id.c19_pick);
		pickButton.setText("Pick " + count);

		pickButton.setOnClickListener(new View.OnClickListener() {
			public void onClick(View v) {
				count ++;
				pickButton.setText("Pick " + count);
			}
		});	
	}
} 

	public void onConfigurationChanged(Configuration newConfig) {
		super.onConfigurationChanged(newConfig);
		setupViews();
	}