Android 安卓:添加片段后,`getSupportFragmentManager()。GetBackBackbackEntryCount()`返回零
我刚刚创建了一个新的Android项目,现在我正试图添加一个片段 问题:在按下手机上的“后退”按钮后,Android 安卓:添加片段后,`getSupportFragmentManager()。GetBackBackbackEntryCount()`返回零,android,android-fragments,Android,Android Fragments,我刚刚创建了一个新的Android项目,现在我正试图添加一个片段 问题:在按下手机上的“后退”按钮后,getSupportFragmentManager().getBackbackEntryCount()返回零,因此不会返回到主活动,为什么 我遵循了可能的解决方案,但它们对我不起作用 @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState);
getSupportFragmentManager().getBackbackEntryCount()
返回零,因此不会返回到主活动,为什么
我遵循了可能的解决方案,但它们对我不起作用
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
setContentView(R.layout.fragment_blank);
// Check that the activity is using the layout version with
// the fragment_container FrameLayout
if (findViewById(R.id.fragment_container) != null) {
// Create a new Fragment to be placed in the activity layout
BlankFragment firstFragment = new BlankFragment();
// In case this activity was started with special instructions from an
// Intent, pass the Intent's extras to the fragment as arguments
firstFragment.setArguments(getIntent().getExtras());
// Add the fragment to the 'fragment_container' FrameLayout
getSupportFragmentManager().beginTransaction().add(R.id.fragment_container, firstFragment).
addToBackStack(null).commit();
getSupportFragmentManager().executePendingTransactions();
}
}
});
}
@Override
public void onBackPressed() {
if(getSupportFragmentManager().getBackStackEntryCount() != 0) {
getSupportFragmentManager().popBackStack();
} else {
super.onBackPressed(); //THIS IS CALLED!!
}
}
编辑1:我想补充一点,打开片段后“返回”时,我会看到我手机的桌面。然后,如果我按下“最近的应用程序”按钮,可以找到应用程序,显示片段的内容,如下所示:
然后,如果我选择它,我会在按下“返回”按钮时得到应用程序
编辑2:以下是整个课程:
package com.example.tirengarfio.myapplication;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v4.app.FragmentManager;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
public class MainActivity extends AppCompatActivity {
final FragmentManager fragmentManager = getSupportFragmentManager();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
setContentView(R.layout.fragment_blank);
// Check that the activity is using the layout version with
// the fragment_container FrameLayout
if (findViewById(R.id.fragment_container) != null) {
// Create a new Fragment to be placed in the activity layout
BlankFragment firstFragment = new BlankFragment();
// In case this activity was started with special instructions from an
// Intent, pass the Intent's extras to the fragment as arguments
firstFragment.setArguments(getIntent().getExtras());
String foo = "foo";
// Add the fragment to the 'fragment_container' FrameLayout
getSupportFragmentManager().beginTransaction().add(R.id.fragment_container, firstFragment).
addToBackStack(foo).commit();
getSupportFragmentManager().executePendingTransactions();
}
}
});
}
@Override
public void onBackPressed() {
if(getSupportFragmentManager().getBackStackEntryCount() != 0) {
getSupportFragmentManager().popBackStack();
} else {
super.onBackPressed();
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
@你能解释一下你的评论吗?我使用的是
addToBackStack
,因此我认为我正在将片段添加到BackStack中,我无法在您的链接内容中找到任何解决我的问题的方法。@FrankN.Stein我添加了一个字符串,但结果是相同的。@FrankN.Stein我编辑了我的问题,也许您觉得它对我有帮助。我发现这是课堂活动,因此getSupportFragmentManager().popBackStack()不运行。@QuangDoan,但我在代码中使用了AppCompatActivity
。我现在要把全班同学都贴在我的问题上。