在 android 中实施 onbackpressed

Question

我有 activity1 带我到 activity2 带我去片段。我想从片段回到活动 2

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

on fragments 获取 backpressed 事件并调用

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

Answer 2

@Override
public void onBackPressed() {
    if (getFragmentManager().getBackStackEntryCount() > 0) {
        getFragmentManager().popBackStack();
    }
    else
        super.onBackPressed();
}

Answer 3

将该片段事务添加到后台堆栈。

Answer 4

从 activity2 添加片段时，像这样将其添加到后台堆栈

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

然后 onBackPressed 检查片段是否存在于后台堆栈中并将其弹出

 @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();
    }
}

在 android 中实施 onbackpressed

implementing onbackpressed in android

android

fragment

android-activity

onbackpressed