在android中实现onbackpressed

Question

我有activity1带我到activity2，让我去片段。我想从片段回到activity2

public void onBackPressed() {
    Intent intent = new Intent(Intent.ACTION_MAIN);
    intent.addCategory(Intent.CATEGORY_HOME);
    intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
    startActivity(intent);
}

Answer 1

{{1}}

Answer 2

片段上的

得到反向事件并调用

getactivity().getsupportfragmentmanager().popbackstack();

Answer 3

从activity2添加片段时，将其添加到backstack，就像这样

getSupportFragmentManager().beginTransaction()
                           .replace(R.id.frame_layout, new SampleFragment())
                           .addToBackStack(SampleFragment.class.getSimpleName())
                           .commit();

onBackPressed检查片段是否存在于backstack中并弹出

 @Override
public void onBackPressed() {
    if(getSupportFragmentManager().getBackStackEntryCount()>0){
        Fragment fragment=getSupportFragmentManager().findFragmentById(R.id.YOUR_FRAME_LAYOUT_ID);
        if(fragment!=null && fragment.getClass().getSimpleName().equalsIgnoreCase(SampleFragment.class.getSimpleName())){
            getSupportFragmentManager().popBackStackImmediate();
        }
    }else {
        super.onBackPressed();
    }
}

Answer 4

将该片段事务添加到backstack。