如何加载在MainActivity上按下手机的背面按钮

我有一个MainActivity已在it.In一个NavigationDrawer抽屉菜单的每个项目，当我从任何的按返回键启动一个新的activity.Now这些活动我最终成为一个空白页面，当我再次按下它时，它会转到主要activity.What我想要直接进入主要活动。如何加载在MainActivity上按下手机的背面按钮

我MainActivity.java：

package com.defcomm.invento; 

import android.support.design.widget.CollapsingToolbarLayout; 
import android.support.design.widget.CoordinatorLayout; 
import android.support.v4.view.ViewPager; 
import android.support.v4.widget.DrawerLayout; 
import android.support.v7.app.ActionBar; 
import android.support.v7.app.ActionBarDrawerToggle; 
import android.support.v7.app.AppCompatActivity; 
import android.os.Bundle; 
import com.defcomm.invento.NavigationDrawerActivity; 
import android.support.v4.widget.NestedScrollView; 
import android.support.v7.widget.RecyclerView; 
import android.support.v7.widget.Toolbar; 
import android.view.Menu; 
import android.view.MenuItem; 

public class INVENTO extends AppCompatActivity { 

private Toolbar toolbar; 
private CoordinatorLayout mCoordinator; 
private CollapsingToolbarLayout mCollapsableLayout; 
private NestedScrollView nestedScrollView; 
private ViewPager mPager; 
@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_new); 
    mCoordinator= (CoordinatorLayout) findViewById(R.id.coordinator_layout); 
    mCollapsableLayout = (CollapsingToolbarLayout) findViewById(R.id.collapsing_toolbar); 
    toolbar= (Toolbar) findViewById(R.id.appbar); 
    setSupportActionBar(toolbar); 
    getSupportActionBar().setDisplayShowHomeEnabled(true); 

    mCollapsableLayout.setTitle(getResources().getString(R.string.app_name)); 
    nestedScrollView= (NestedScrollView) findViewById(R.id.rvToDoList); 
    mCollapsableLayout.setExpandedTitleTextAppearance(R.style.ExpandedTitleTextAppearence); 
    mCollapsableLayout.setCollapsedTitleTextColor(getResources().getColor(R.color.textColor)); 
    NavigationDrawerActivity drawerFragment= (NavigationDrawerActivity) getSupportFragmentManager(). 
      findFragmentById(R.id.navigation_drawer); 
     drawerFragment.setUp(R.id.navigation_drawer, (DrawerLayout) findViewById(R.id.drawerlayout), toolbar); 


} 
@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_invento, 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); 
} 
}

我NavigationDrawer.java1：

package com.defcomm.invento; 


import android.content.Context; 
import android.content.Intent; 
import android.content.SharedPreferences; 
import android.content.res.Configuration; 
import android.os.Bundle; 
import android.support.annotation.Nullable; 
import android.support.design.widget.CoordinatorLayout; 
import android.support.v4.app.Fragment; 
import android.support.v4.app.FragmentActivity; 
import android.support.v4.widget.DrawerLayout; 
import android.support.v7.app.ActionBar; 
import android.support.v7.app.ActionBarDrawerToggle; 
import android.support.v7.app.AppCompatActivity; 
import android.support.v7.widget.LinearLayoutManager; 
import android.support.v7.widget.RecyclerView; 
import android.support.v7.widget.Toolbar; 
import android.view.LayoutInflater; 
import android.support.design.widget.CollapsingToolbarLayout; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.LinearLayout; 

import java.util.ArrayList; 
import java.util.List;

公共类NavigationDrawerActivity扩展片段实现MyAdapter.clickListener {

private ActionBarDrawerToggle mdrawerToggle; 
private DrawerLayout mdrawerLayout; 
private boolean mUserLearnedState; 
private MyAdapter adapter; 
private CoordinatorLayout mcoordinator; 
private RecyclerView recyclerView; 
private CollapsingToolbarLayout collapsingToolbarLayout; 
View containerId; 
public static final String file_pref_name = "Testpef"; 
public static final String KEY_USER_VALUE = "user_learned_drawer"; 
private boolean mfromSavedInstanceState; 

public NavigationDrawerActivity() { 
    // Required empty public constructor 
} 

@Override 
public void onCreate(@Nullable Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    mUserLearnedState = Boolean.valueOf(readPreference(getActivity(), KEY_USER_VALUE, "false")); 
    if (savedInstanceState != null) { 
     mfromSavedInstanceState = true; 
    } 

} 

@Override 
public View onCreateView(LayoutInflater inflater, ViewGroup container, 
         Bundle savedInstanceState) { 
    // Inflate the layout for this fragment 
    View layout=inflater.inflate(R.layout.fragment_navigation_drawer, container, false); 
    recyclerView= (RecyclerView) layout.findViewById(R.id.recycler); 
    adapter=new MyAdapter(getActivity(),getdata()); 
    adapter.setClicklistener(this); 
    recyclerView.setAdapter(adapter); 
    recyclerView.setLayoutManager(new LinearLayoutManager(getActivity())); 
    return layout; 

} 
public static List<ListItems> getdata(){ 
    List<ListItems> nav_data=new ArrayList<>(); 
    int[] icons={R.drawable.variable,R.drawable.ignore}; 
    String[] texts={"Coding","Hacking"}; 
    for(int i=0;i<icons.length&&i<icons.length;i++){ 
     ListItems current=new ListItems(); 
     current.iconId=icons[i]; 
     current.IconName=texts[i]; 
     nav_data.add(current); 
    } 
    return nav_data; 
} 

public void setUp(final int fragmentId, DrawerLayout drawerlayout, final Toolbar toolbar) { 
    mdrawerLayout = drawerlayout; 
    containerId = getActivity().findViewById(fragmentId); 
    mdrawerToggle = new ActionBarDrawerToggle(getActivity(), drawerlayout, toolbar, 
      R.string.drawer_open, R.string.drawer_close) { 
     @Override 
     public void onDrawerOpened(View drawerView) { 
      super.onDrawerOpened(drawerView); 
      if (!mUserLearnedState) { 
       mUserLearnedState = true; 
       saveToPreference(getActivity(), KEY_USER_VALUE, mUserLearnedState + ""); 
      } 
      getActivity().invalidateOptionsMenu(); 
     } 

     @Override 
     public void onDrawerClosed(View drawerView) { 
      super.onDrawerClosed(drawerView); 
      getActivity().invalidateOptionsMenu(); 

     } 

     @Override 
     public void onDrawerSlide(View drawerView, float slideOffset) { 
      if (slideOffset < 0.5f) { 
       toolbar.setAlpha(1 - slideOffset); 
      } 
     } 
    }; 
    if (!mUserLearnedState && !mfromSavedInstanceState) { 
     mdrawerLayout.openDrawer(containerId); 
    } 

    mdrawerLayout.setDrawerListener(mdrawerToggle); 
    mdrawerLayout.post(new Runnable() { 
     @Override 
     public void run() { 
      mdrawerToggle.syncState(); 

     } 
    }); 

} 


public static void saveToPreference(Context context, String preferenceName, String preferenceValue) { 
    SharedPreferences shared = context.getSharedPreferences(file_pref_name, Context.MODE_PRIVATE); 
    SharedPreferences.Editor editor = shared.edit(); 
    editor.putString(preferenceName, preferenceValue); 
    editor.apply(); 
} 

public static String readPreference(Context context, String preferenceName, String defaultValue) { 
    SharedPreferences share = context.getSharedPreferences(file_pref_name, Context.MODE_PRIVATE); 
    return share.getString(preferenceName, defaultValue); 
} 

@Override 
public void ItemCLick(View view, int position) { 
    if(position==0){ 
     startActivity(new Intent(getActivity(),Coding.class)); 
    } 
    if(position==1){ 
     startActivity(new Intent(getActivity(),Hacking.class)); 
    } 

    } 
}

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?> 
<manifest xmlns:android="http://schemas.android.com/apk/res/android" 
package="com.defcomm.invento" > 

<application 
    android:allowBackup="true" 
    android:icon="@mipmap/ic_launcher" 
    android:label="@string/app_name" 
    android:theme="@style/AppTheme" > 
    <activity 
     android:name=".INVENTO" 
     android:label="@string/app_name" > 
     <intent-filter> 
      <action android:name="android.intent.action.MAIN" /> 

      <category android:name="android.intent.category.LAUNCHER" /> 
     </intent-filter> 
    </activity> 
    <activity 
     android:name=".Coding" 
     android:label="@string/title_activity_coding" > 
    </activity> 
    <activity 
     android:name=".Hacking" 
     android:label="@string/title_activity_hacking" > 
    </activity> 
</application>

来源

2015-10-06 Midhun

您至少可以检查您的MainActivity是否设置为从NavigationDrawer启动的其他活动的父活动。请参阅[文档]（https://developer.android.com/training/implementing-navigation/ancestral.html）。也可以在这里发布你的AndroidManifest.xml以及它可能与问题有关的其他内容。还有你重写onBackPressed（）在其他活动？如果是，如何？最后，你是说底部或Action Bar中的后退按钮？ –

通过后退按钮，我的意思是手机的物理按钮。由于我刚接触android，我想知道如何将主要活动设置为其他活动的父活动。对于'AndroidManifest.xml'我在这里编辑帖子。谢谢。 – Midhun

我的猜测是你的代码会添加一个空的片段（或活动）来支持堆栈。也许你在你的应用程序启动时没有看到这个，因为你的onSomething生命周期方法中加载了片段或其他活动。但是当你回去时你会看到它。此外，将“NavigationDrawerActivity”重命名为“NavigationDrawerFragment”，因为它不是活动的片段。 – Jens

你可以试试这个。

@Override 
public void onBackPressed() { 

    startActivity(new Intent(this,MainActivity.class)); 
    this.finish(); 
}

来源

2015-10-06 07:01:17 ButchxD

这对我来说很有效，但是我们为什么必须这样做吗？它不应该自动设置为启动父级活动吗？ – juil

试试这个

Intent intent = new Intent(this, MainActivity.class); 
     intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK); 
     startActivity(intent);

这将关闭所有其他活动，并开始MainActivity

来源

2015-10-06 07:42:10 Prakhar

这将关闭抽屉时，它的开放和回压，而不是带你回到以前的活动（或退出）。

DrawerLayout drawer... 

@Override 
public void onBackPressed() { 
    // TODO Auto-generated method stub 

    if(drawer.isDrawerOpen(Gravity.LEFT)){ 
     drawer.closeDrawer(Gravity.LEFT); 
    startActivity(new Intent(CurrentActivity.this , MainActivity.class)) 
    finish(); 

    }else{ 
     super.onBackPressed(); 
    } 
}

来源

2015-10-06 13:48:16 KishuDroid

如何加载在MainActivity上按下手机的背面按钮

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