android包变为0

Question

我有一个recyclerview，当点击它进入相应的活动时。我通过使用bundle绑定它们然后将它放入intent中来传递它们的位置。我从各个类中检索数据。这些活动中的每一个都有viewpager在其中那么我把那个位置放在活动中创建的ImagePagerAdapter对象中。图像完全加载到viewpager中。我在这些活动中有一个按钮，它会进入不同的活动，当我尝试导航回到活动但是 应用程序崩溃。这是出现的错误： 错误：

01-27 03:40:40.220 5043-5043/com.example.sabudaniel61.ktdc E/AndroidRuntime: java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.sabudaniel61.ktdc/com.example.sabudaniel61.ktdc.NandFragment}: java.lang.NullPointerException
01-27 03:40:40.220 5043-5043/com.example.sabudaniel61.ktdc E/AndroidRuntime:     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2252)
01-27 03:40:40.220 5043-5043/com.example.sabudaniel61.ktdc E/AndroidRuntime:     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2306)
01-27 03:40:40.220 5043-5043/com.example.sabudaniel61.ktdc E/AndroidRuntime:     at android.app.ActivityThread.access$700(ActivityThread.java:153)
01-27 03:40:40.220 5043-5043/com.example.sabudaniel61.ktdc E/AndroidRuntime:     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1286)
01-27 03:40:40.220 5043-5043/com.example.sabudaniel61.ktdc E/AndroidRuntime:     at android.os.Handler.dispatchMessage(Handler.java:99)
01-27 03:40:40.220 5043-5043/com.example.sabudaniel61.ktdc E/AndroidRuntime:     at android.os.Looper.loop(Looper.java:176)
01-27 03:40:40.220 5043-5043/com.example.sabudaniel61.ktdc E/AndroidRuntime:     at android.app.ActivityThread.main(ActivityThread.java:5302)
01-27 03:40:40.220 5043-5043/com.example.sabudaniel61.ktdc E/AndroidRuntime:     at java.lang.reflect.Method.invokeNative(Native Method)
01-27 03:40:40.220 5043-5043/com.example.sabudaniel61.ktdc E/AndroidRuntime:     at java.lang.reflect.Method.invoke(Method.java:511)
01-27 03:40:40.220 5043-5043/com.example.sabudaniel61.ktdc E/AndroidRuntime:     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1102)
01-27 03:40:40.220 5043-5043/com.example.sabudaniel61.ktdc E/AndroidRuntime:     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:869)
01-27 03:40:40.220 5043-5043/com.example.sabudaniel61.ktdc E/AndroidRuntime:     at dalvik.system.NativeStart.main(Native Method)
01-27 03:40:40.220 5043-5043/com.example.sabudaniel61.ktdc E/AndroidRuntime:  Caused by: java.lang.NullPointerException
01-27 03:40:40.220 5043-5043/com.example.sabudaniel61.ktdc E/AndroidRuntime:     at com.example.sabudaniel61.ktdc.NandFragment.onCreate(NandFragment.java:66)
01-27 03:40:40.220 5043-5043/com.example.sabudaniel61.ktdc E/AndroidRuntime:     at android.app.Activity.performCreate(Activity.java:5326)
01-27 03:40:40.220 5043-5043/com.example.sabudaniel61.ktdc E/AndroidRuntime:     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1097)
01-27 03:40:40.220 5043-5043/com.example.sabudaniel61.ktdc E/AndroidRuntime:     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2215)
01-27 03:40:40.220 5043-5043/com.example.sabudaniel61.ktdc E/AndroidRuntime:     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2306) 
01-27 03:40:40.220 5043-5043/com.example.sabudaniel61.ktdc E/AndroidRuntime:     at android.app.ActivityThread.access$700(ActivityThread.java:153) 
01-27 03:40:40.220 5043-5043/com.example.sabudaniel61.ktdc E/AndroidRuntime:     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1286) 
01-27 03:40:40.220 5043-5043/com.example.sabudaniel61.ktdc E/AndroidRuntime:     at android.os.Handler.dispatchMessage(Handler.java:99) 
01-27 03:40:40.220 5043-5043/com.example.sabudaniel61.ktdc E/AndroidRuntime:     at android.os.Looper.loop(Looper.java:176) 
01-27 03:40:40.220 5043-5043/com.example.sabudaniel61.ktdc E/AndroidRuntime:     at android.app.ActivityThread.main(ActivityThread.java:5302) 
01-27 03:40:40.220 5043-5043/com.example.sabudaniel61.ktdc E/AndroidRuntime:     at java.lang.reflect.Method.invokeNative(Native Method) 
01-27 03:40:40.220 5043-5043/com.example.sabudaniel61.ktdc E/AndroidRuntime:     at java.lang.reflect.Method.invoke(Method.java:511) 
01-27 03:40:40.220 5043-5043/com.example.sabudaniel61.ktdc E/AndroidRuntime:     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1102) 
01-27 03:40:40.220 5043-5043/com.example.sabudaniel61.ktdc E/AndroidRuntime:     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:869) 
01-27 03:40:40.220 5043-5043/com.example.sabudaniel61.ktdc E/AndroidRuntime:     at dalvik.system.NativeStart.main(Native Method) 

RecyclerAdapter.java：

    itemLayoutView.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            position = getAdapterPosition();
            switch(position) {
                case 0:
                    Intent intent = new Intent(context, AranyaFragment.class);
                    Bundle a = new Bundle();
                    a.putInt("Aranya", position);
                    intent.putExtras(a);
                    intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                    context.startActivity(intent);
                    break;
                case 1:
                    Intent intent1 = new Intent(context, BolgattyFragment.class);
                    Bundle b = new Bundle();
                    b.putInt("Bolg", position);
                    intent1.putExtras(b);
                    intent1.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                    context.startActivity(intent1);
                    break;
                case 2:
                    Intent intent2 = new Intent(context, MascotFragment.class);
                    intent2.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                    Bundle c = new Bundle();
                    c.putInt("Mas", position);
                    intent2.putExtras(c);
                    context.startActivity(intent2);
                    break;
                case 3:
                    Intent intent3 = new Intent(context, WaterScapes.class);
                    Bundle d = new Bundle();
                    d.putInt("Water", position);
                    intent3.putExtras(d);
                    intent3.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                    context.startActivity(intent3);
                    break;
                case 4:
                    Intent intent4 = new Intent(context, SamudraFragment.class);
                    Bundle e = new Bundle();
                    e.putInt("Samudra", position);
                    intent4.putExtras(e);
                    intent4.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                    context.startActivity(intent4);
                    break;
                case 5:
                    Intent intent5 = new Intent(context, GoldenFragment.class);
                    Bundle f = new Bundle();
                    f.putInt("Gold", position);
                    intent5.putExtras(f);

                    intent5.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                    context.startActivity(intent5);
                    break;
                case 6:
                    Intent intent6 = new Intent(context, RainFragment.class);
                    Bundle g = new Bundle();
                    g.putInt("Rain", position);
                    intent6.putExtras(g);
                    intent6.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                    context.startActivity(intent6);
                    break;
                case 7:
                    Intent intent7 = new Intent(context, PeriyarFragment.class);
                    Bundle h = new Bundle();
                    h.putInt("Periyar", position);
                    intent7.putExtras(h);
                    intent7.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                    context.startActivity(intent7);
                    break;
                case 8:
                    Intent intent8 = new Intent(context, PepperFragment.class);
                    Bundle i = new Bundle();
                    i.putInt("Pepper", position);
                    intent8.putExtras(i);
                    intent8.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                    context.startActivity(intent8);
                    break;
                case 9:
                    Intent intent9 = new Intent(context, NandFragment.class);
                    Bundle j = new Bundle();
                    j.putInt("Nand", position);
                    intent9.putExtras(j);
                    intent9.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                    context.startActivity(intent9);
                    break;
                case 10:
                    Intent intent10 = new Intent(context, TamarFragment.class);
                    Bundle k = new Bundle();
                    k.putInt("Tamar", position);
                    intent10.putExtras(k);
                    intent10.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                    context.startActivity(intent10);
                    break;
            }
        }
    });
}

NandFragment.java（实际上不是故障）：在下面的代码中，我使用

检索位置

Bundle b=getIntent().getExtras(); 
pos= b.getInt("Nand");

该按钮转到另一个活动，当我尝试返回应用程序崩溃时。错误发生在

pos= b.getInt("Nand");

public class NandFragment extends AppCompatActivity implements OnMapReadyCallback {
 @Override
    protected void onCreate( Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.nandanamlayout);
        Bundle b=getIntent().getExtras();
        pos= b.getInt("Nand");
        Button button1;
        button1=(Button) findViewById(R.id.nrrooms);
        button1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(getApplicationContext(), NandRooms.class);
                startActivity(intent);
            }
        });
ViewPager viewPager = (ViewPager) findViewById(R.id.vpfragment9);

        ImagePagerAdapter pagerAdapter=new ImagePagerAdapter(this,pos);
        viewPager.setAdapter(pagerAdapter);
        viewPager.setPageTransformer(true, new ParallaxPageTransformer());}}

NandRooms.java：

public class NandRooms extends AppCompatActivity {
protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.rooms);
  Toolbar toolbar=(Toolbar) findViewById(R.id.rooms);
        setSupportActionBar(toolbar);
        getSupportActionBar().setTitle("Rooms");
        getSupportActionBar().setHomeButtonEnabled(true);
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);}}

如果你还不明白，请告诉我......

Answer 1

您的问题是，当您点击向上按钮时，您不会像第一次导航到NandFragment活动时那样发送任何额外内容。因此，当您使用向上按钮返回活动时，getIntent().getExtras()将返回null，因为没有已发送的Extras。处理此问题的方法是覆盖向上操作按钮，然后处理＆＃34;返回导航＆＃34;你自己，沿途插入你的演员。为此，您需要覆盖onOptionsItemSelected()并查找android.R.id.home操作。然后你会做这样的事情：

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    int id = item.getItemId();
    switch(id) {
        case android.R.id.home:
            Intent upIntent = new Intent(this, NandFragment.class);
            //put in your extras here...
            startActivity(upIntent);

            //return true to let the OS know you handled this action yourself
            return true;
    }
    return false;
}

Answer 2

在你获得额外价值之前，请先检查你是否先拥有它，否则如果它不存在你就会收到错误。

   if (getIntent().hasExtra("Nand")) {
       Bundle b=getIntent().getExtras();
       pos= b.getInt("Nand");
   }
   else{
       Log.d("TAG", "Bundle is not set");
   }