ActionBar中的Home Up按钮不起作用

Question

I've a problem with the Home Up Button in ActionBar . I'm in a PreferenceActivity and in the onCreate i've put the following code:

    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
        getActionBar().setDisplayHomeAsUpEnabled(true);
    }

When I run my application it shows the Up Button but when I click on it nothing happens. So I put this code in the AndroidManifest :

    <activity android:name="com.example.mypackage.SystemInfo">
      <meta-data
        android:name="android.support.PARENT_ACTIVITY"
        android:value="com.simonedev.androtools.MainActivity" />
    </activity>

But I still have the same problem. How can I solve it? Where is the problem?

Answer 1

The wrong way up

You shouldn't use

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    super.onOptionsItemSelected(item);
    switch(item.getItemId()) {
        case android.R.id.home:
        //Do not use the following
        //PreferenceActivity.this.onBackPressed(); 
        //or
        //finish();
        break;
    }
    return true;   
}

The proper way up

But instead follow this presentation and google guidelines

The Manifest should add 1 more attribute

<activity android:name="com.example.mypackage.SystemInfo"
    android:parentActivityName="com.simonedev.androtools.MainActivity" >
  <meta-data
    android:name="android.support.PARENT_ACTIVITY"
    android:value="com.simonedev.androtools.MainActivity" />
</activity>

Copied code from the presentation : this would be the simple case

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    super.onOptionsItemSelected(item);
    switch(item.getItemId()) {
        case android.R.id.home:
        NavUtils.navigateUpFromSameTask(this);
        break;
    }
    return true;   
}

I invite you to read the whole presentation for other more complex cases

Answer 2

Add this method in your class, but outside the onCreate() method

@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.action_bar, menu);
setTitle("");
return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
 super.onOptionsItemSelected(item);
 switch(item.getItemId())
 {

case android.R.id.home:
PreferenceActivity.this.onBackPressed(); 
break;


 }
 return true;   
 }

Now, after your comments. you may have to create a file called action_bar.xml in your res/menu folder, and add the following to it

 <menu xmlns:android="http://schemas.android.com/apk/res/android">
 </menu>