如何从特定活动返回导航抽屉活动

时间：2017-11-09 19:07:50

标签： java android navigation-drawer solver challenge-response

当我点击我的导航抽屉（HomePage.java）中的帐户转移到帐户活动（account.java）。当我尝试点击返回帐户（account.java）我的应用程序停止。让我看看谁的专业编码器会帮助我。把它作为挑战。我尝试了很多，但没有任何帮助我。完全看到我的问题和我的代码。我是Android的新手帮我。我为这个错误而生气。

11-10 00:03:56.739 12243-12243/com.example.hppc.homeservices E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.hppc.homeservices, PID: 12243
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.hppc.homeservices/com.example.hppc.homeservices.HomePage}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.CharSequence android.os.Bundle.getCharSequence(java.lang.String)' on a null object reference
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2817)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2892)
        at android.app.ActivityThread.-wrap11(Unknown Source:0)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1593)
        at android.os.Handler.dispatchMessage(Handler.java:105)
        at android.os.Looper.loop(Looper.java:164)
        at android.app.ActivityThread.main(ActivityThread.java:6541)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.CharSequence android.os.Bundle.getCharSequence(java.lang.String)' on a null object reference
        at com.example.hppc.homeservices.HomePage.onCreate(HomePage.java:33)
        at android.app.Activity.performCreate(Activity.java:6975)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1213)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2770)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2892) 
        at android.app.ActivityThread.-wrap11(Unknown Source:0) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1593) 
        at android.os.Handler.dispatchMessage(Handler.java:105) 
        at android.os.Looper.loop(Looper.java:164) 
        at android.app.ActivityThread.main(ActivityThread.java:6541) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767) 

NavigationDrawer Activity.java（HomePage.java）

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_home_page);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);
    Bundle b = getIntent().getExtras();
    NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
    navigationView.setNavigationItemSelectedListener(this);
    TextView txtProfileName = (TextView) navigationView.getHeaderView(0).findViewById(R.id.tvEmailHome);
    txtProfileName.setText(b.getCharSequence("Email"));
    FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
    fab.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                    .setAction("Action", null).show();
        }
    });

    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
            this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
    drawer.addDrawerListener(toggle);
    toggle.syncState();
}

@Override
public void onBackPressed() {
    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    if (drawer.isDrawerOpen(GravityCompat.START)) {
        drawer.closeDrawer(GravityCompat.START);
    } 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.home_page, 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);
}

@SuppressWarnings("StatementWithEmptyBody")
@Override
public boolean onNavigationItemSelected(MenuItem item) {
    // Handle navigation view item clicks here.
    int id = item.getItemId();

    if (id == R.id.nav_Account) {
        startActivity(new Intent(HomePage.this,Account.class));
        finish();

    } if (id == R.id.nav_Services) {


    } if (id == R.id.nav_settings) {

    } if (id == R.id.nav_Help) {

    } if (id == R.id.LogOut) {
        FirebaseAuth.getInstance().signOut();
        startActivity(new Intent(HomePage.this,MainActivity.class));
        finish();

    } if (id == R.id.nav_share) {

    } if (id == R.id.nav_send) {

    }

    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    drawer.closeDrawer(GravityCompat.START);
    return true;

Account.java（导航栏中的我的帐户）

private DatabaseReference databaseReference;
private ListView details;
private ArrayList<String> account = new ArrayList<>();
FirebaseUser user;

String uid;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_account);
    details=(ListView)findViewById(R.id.listview);
    user = FirebaseAuth.getInstance().getCurrentUser();
    uid = user.getUid();

    final ArrayAdapter<String> arrayAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, account);

    details.setAdapter(arrayAdapter);

    databaseReference = FirebaseDatabase.getInstance().getReference();

    databaseReference.addChildEventListener(new ChildEventListener() {
        @Override
        public void onChildAdded(DataSnapshot dataSnapshot, String s) {
            String user_name = dataSnapshot.child("Name").getValue(String.class);
            String user_email = dataSnapshot.child("Email").getValue(String.class);
            String user_phone = dataSnapshot.child("Phone").getValue(String.class);
            if (user.getEmail().equalsIgnoreCase(user_email)) {
                account.add("Name :" + user_name);
                account.add("Email ID :" + user_email);
                account.add("Phone Number :" + user_phone);

                arrayAdapter.notifyDataSetChanged();
            }
        }
        @Override
        public void onChildChanged(DataSnapshot dataSnapshot, String s) {

        }

        @Override
        public void onChildRemoved(DataSnapshot dataSnapshot) {

        }

        @Override
        public void onChildMoved(DataSnapshot dataSnapshot, String s) {

        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });
   getSupportActionBar().setDisplayShowHomeEnabled(true);
   getSupportActionBar().setDisplayHomeAsUpEnabled(true);
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    int id = item.getItemId();

    if(id==android.R.id.home){
        Intent mainInten = new Intent(this, HomePage.class);
        this.startActivity(mainInten);
        //this.finish();
        //onBackPressed();
    }
    return super.onOptionsItemSelected(item);
}

public void checking(View view) {
    startActivity(new Intent(Account.this,MyAccount.class));
    finish();
}

当我点击导航抽屉中的帐户时，我正在转移到“帐户”活动，但当我尝试在该帐户活动顶部的“帐户”活动中点击goback图标时，我的应用程序就会停止。

1 个答案:

答案 0 :(得分：0)

我遇到了同样的问题。当我删除动作栏时，它完美无缺。从Account.java中删除以下行。

   getSupportActionBar().setDisplayShowHomeEnabled(true);
   getSupportActionBar().setDisplayHomeAsUpEnabled(true);

作为建议，不要使用导航抽屉活动。使用片段比活动容易得多。您可以使用FragmentTransaction.addToBackStack(null);方法轻松返回到先前的片段。 我参考了这个视频教程。它可能会有所帮助。 https://www.youtube.com/watch?v=-SUvA1fXaKw

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