How to implement the Android ActionBar back button?

问题

I have an activity with a listview. When the user click the item, the item \"viewer\" opens:

List1.setOnItemClickListener(new OnItemClickListener() {
    @Override
    public void onItemClick(AdapterView<?> arg0, View arg1, int arg2,long arg3) {

        Intent nextScreen = new Intent(context,ServicesViewActivity.class);
        String[] Service = (String[])List1.getItemAtPosition(arg2);

        //Sending data to another Activity
        nextScreen.putExtra(\"data\", datainfo);
        startActivityForResult(nextScreen,0);
        overridePendingTransition(R.anim.right_enter, R.anim.left_exit);
    }
});

This works fine, but on the actionbar the back arrow next to the app icon doesn\'t get activated. Am I missing something?

回答1:

Selvin already posted the right answer, here is only the solution in pretty code ;-)

public class ServicesViewActivity extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        // etc...
        getActionBar().setDisplayHomeAsUpEnabled(true);
    }

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

The function NavUtils.navigateUpFromSameTask(this) requires you to define the parent activity in the AndroidManifest.xml file

    <activity android:name="com.example.ServicesViewActivity" >
            <meta-data
            android:name="android.support.PARENT_ACTIVITY"
            android:value="com.example.ParentActivity" />
    </activity>

http://developer.android.com/design/patterns/navigation.html#up-vs-back

回答2:

Make sure your the ActionBar Home Button is enabled in the Activity:

Android, API 5+:

@Override
public void onBackPressed() {
     ...
     super.onBackPressed();
}

ActionBarSherlock and App-Compat, API 7+:

@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
    ...
    getSupportActionBar().setDisplayHomeAsUpEnabled(true);
}

Android, API 11+:

@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
    ...
    getActionBar().setDisplayHomeAsUpEnabled(true);
}

Example MainActivity that extends ActionBarActivity:

public class MainActivity extends ActionBarActivity {
    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        // Back button
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
        case android.R.id.home: 
            // API 5+ solution
            onBackPressed();
            return true;

        default:
            return super.onOptionsItemSelected(item);
        }
    }
}

This way all the activities you want can have the backpress.

Android, API 16+:

http://developer.android.com/training/implementing-navigation/ancestral.html

AndroidManifest.xml:

<application ... >
    ...
    <!-- The main/home activity (it has no parent activity) -->
    <activity
        android:name="com.example.myfirstapp.MainActivity" ...>
        ...
    </activity>
    <!-- A child of the main activity -->
    <activity
        android:name="com.example.myfirstapp.DisplayMessageActivity"
        android:label="@string/title_activity_display_message"
        android:parentActivityName="com.example.myfirstapp.MainActivity" >
        <!-- The meta-data element is needed for versions lower than 4.1 -->
        <meta-data
            android:name="android.support.PARENT_ACTIVITY"
            android:value="com.example.myfirstapp.MainActivity" />
    </activity>
</application>

Example MainActivity that extends ActionBarActivity:

public class MainActivity extends ActionBarActivity {
    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        // Back button
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
        // Respond to the action bar's Up/Home button
        case android.R.id.home:
            NavUtils.navigateUpFromSameTask(this);
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
}

回答3:

To enable the ActionBar back button you obviously need a ActionBar in your Activity. This is set by the theme you are using. You can set the theme for your Activity in the AndroidManfiest.xml. If you are using e.g the @android:style/Theme.NoTitleBar theme, you dont have a ActionBar. In this case the call to getActionBar() will return null. So make sure you have a ActionBar first.

Next step is to set the android:parentActivityName to the activity you want to navigate if you press the back button. This should be done in the AndroidManfiest.xml too.

Now you can enable the back button in the onCreate method of your "child" activity.

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    getActionBar().setDisplayHomeAsUpEnabled(true);
}

Now you should implement the logic for the back button. You simply override the onOptionsItemSelected method in your "child" activity and check for the id of the back button which is android.R.id.home.

Now you can fire the method NavUtils.navigateUpFromSameTask(this); BUT if you dont have specified the android:parentActivityName in you AndroidManfiest.xml this will crash your app.

Sometimes this is what you want because its reminds you that you forgot "something" but if you want to prevent this, you can check if your activity has a parent using the getParentActivityIntent() method. If this returns null, you dont have specified the parent.

In this case you can fire the onBackPressed() method that does basically the same as if the user would press the back button on the device. A good implementation that never crashs you app would be

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
        case android.R.id.home:
            if (getParentActivityIntent() == null) {
                Log.i(TAG, "You have forgotten to specify the parentActivityName in the AndroidManifest!");
                onBackPressed();
            } else {
                NavUtils.navigateUpFromSameTask(this);
            }
            return true;
        default:
            return super.onOptionsItemSelected(item);
    }
}

Please note that the animation that the user sees is different between NavUtils.navigateUpFromSameTask(this); and onBackPressed().

It is up to you wich road you take but i found the solution helpful, especially if you use a base class for all of your activities.

回答4:

AndroidManifest file:

    <activity android:name=".activity.DetailsActivity">
        <meta-data
            android:name="android.support.PARENT_ACTIVITY"
            android:value="br.com.halyson.materialdesign.activity.HomeActivity" />
    </activity>

add in DetailsActivity:

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);   
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);
    getSupportActionBar().setDisplayHomeAsUpEnabled(true);
}

it's work :]

回答5:

Android Annotations:

@OptionsItem(android.R.id.home)
void homeSelected() {
    onBackPressed();
}

Source: https://github.com/excilys/androidannotations

回答6:

I think onSupportNavigateUp() is simplest and best way to do so

check the code in this link Click here for complete code

回答7:

https://stackoverflow.com/a/46903870/4489222

To achieved this, there are simply two steps,

Step 1: Go to AndroidManifest.xml and in the add the parameter in tag - android:parentActivityName=".home.HomeActivity"

example :

 <activity
    android:name=".home.ActivityDetail"
    android:parentActivityName=".home.HomeActivity"
    android:screenOrientation="portrait" />

Step 2: in ActivityDetail add your action for previous page/activity

example :

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

回答8:

getSupportActionBar().setDisplayHomeAsUpEnabled(true);

in onCreated method for the new apis.

回答9:

In the OnCreate method add this:

if (getSupportActionBar() != null)
    {
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
    }

Then add this method:

@Override
public boolean onSupportNavigateUp() {
    onBackPressed();
    return true;
}

回答10:

If you are using Toolbar, I was facing the same issue. I solved by following these two steps

In the AndroidManifest.xml

<activity android:name=".activity.SecondActivity" android:parentActivityName=".activity.MainActivity"/>

In the SecondActivity, add these...

Toolbar toolbar = findViewById(R.id.second_toolbar);
setSupportActionBar(toolbar);
getSupportActionBar().setDisplayShowTitleEnabled(false);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);

回答11:

Following Steps are much enough to back button:

Step 1: This code should be in Manifest.xml

<activity android:name=".activity.ChildActivity"
        android:parentActivityName=".activity.ParentActivity"
        android:screenOrientation="portrait">
        <meta-data
            android:name="android.support.PARENT_ACTIVITY"
            android:value=".activity.ParentActivity" /></activity>

Step 2: You won't give

finish();

in your Parent Activity while starting Child Activity.

Step 3: If you need to come back to Parent Activity from Child Activity, Then you just give this code for Child Activity.

startActivity(new Intent(ParentActivity.this, ChildActivity.class));

来源：https://stackoverflow.com/questions/10108774/how-to-implement-the-android-actionbar-back-button

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java

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android-3.0-honeycomb