Android 程式开发：（九）使用活动栏 —— 9.3自定义ActionBar项目和程序图标

在上一节中，菜单选项是没有文字的。如果想要同时显示图标和文字，可以一起使用“|”和MenuItem.SHOW_AS_ACTION_WITH_TEXT常量。

[java]
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MenuItem mnu1 = menu.add(0,0,
0,"Item 1");

{
mnu1.setIcon(R.drawable.ic_launcher);
mnu1.setShowAsAction(
MenuItem.SHOW_AS_ACTION_IF_ROOM |
MenuItem.SHOW_AS_ACTION_WITH_TEXT);
}

[java] 
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private boolean MenuChoice(MenuItem item) 
    {          
        switch (item.getItemId()) { 
        case  android.R.id.home:  

            Toast.makeText(this,  
                "You clicked on the Application icon",  
                Toast.LENGTH_LONG).show();  
            return true; 
        case 0: 
            Toast.makeText(this, 
"You clicked on Item 1",   
                Toast.LENGTH_LONG).show();  
            return true; 
        case 1: 
           ......  
    }      

private boolean MenuChoice(MenuItem item)
    {        
        switch (item.getItemId()) {
        case  android.R.id.home:
            Toast.makeText(this, 
                "You clicked on the Application icon", 
                Toast.LENGTH_LONG).show();
            return true;
        case 0:
            Toast.makeText(this, "You clicked on Item 1", 
                Toast.LENGTH_LONG).show();
            return true;
        case 1:
           ......
    }

如果想让应用图标能被点击，我们需要调用setDisplayHomeAsUpEnable()方法：

[java]
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/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);

ActionBar actionBar = getActionBar();
actionBar.setDisplayHomeAsUpEnabled(true);
//actionBar.hide();
//actionBar.show(); //---show it again---
}

[java] 
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case  android.R.id.home: 
    Toast.makeText(this,   
        "You clicked on the Application icon",  
        Toast.LENGTH_LONG).show();  
  
    Intent i = new Intent(this, MyActionBarActivity.class); 
    i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);  
    startActivity(i);  
  
    return true; 

        case  android.R.id.home:
            Toast.makeText(this, 
                "You clicked on the Application icon", 
                Toast.LENGTH_LONG).show();

            Intent i = new Intent(this, MyActionBarActivity.class);
            i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
            startActivity(i);

            return true;

使用Intent.FLAG_ACTIVITY_CLEAR_TOP标识，可以确保当点击应用图标的时候，在“返回栈”里面的那些activity都会被清除掉。使用这种方法，如果用户点击返回键，其他的activity将不会再显示出来。