如何将数据从我的intent.putExtra传递给新的活动，这是一个tablayout？我尝试了很多方法，但当我滑动到标签的另一个位置时数据不会加上我会崩溃。
这是我的代码
customAdapter.java
这段代码来自我的recyclerview我添加了一个onClickListener并使用toast我能够测试从我的数据库显示相应数据的项目，这很好，因为它告诉我我已成功从我的数据库获取数据我点击了。但现在我希望它将它们的值从我的数据库传递到另一个活动，但它不会显示任何内容。
请注意onClick（）方法
public static class MyViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener{
TextView textViewTerm;
List<DataModel> items = new ArrayList<DataModel>();
Context context;
public MyViewHolder(View itemView, Context context, List<DataModel> items) {
super(itemView);
this.items = items;
this.context = context;
itemView.setOnClickListener(this);
this.textViewTerm = (TextView) itemView.findViewById(R.id.textViewTerm);
}
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
int position = getAdapterPosition();
DataModel item = this.items.get(position);
Toast.makeText(context, "ID number: "+item.getId() +" is selected", Toast.LENGTH_SHORT).show();
Intent i = new Intent(this.context,My_Notes_View_Main.class);
i.putExtra("note_id",item.getId());
i.putExtra("note_def",item.getDefinition());
i.putExtra("note_syntax",item.getSyntax());
i.putExtra("note_code", item.getCode());
this.context.startActivity(i);
}
}
这是我的活动，其中包含tablayout 我尝试添加一个if / else语句，如果它们的位置改变了textView值，则替换它从另一个activity获取的内容。它在onTabSelectedListener（）内，但每当我从另一个位置改变时都会导致崩溃。
package com.zaid.recyclerviewsqlite.viewNotes;
import android.os.Bundle; import android.support.design.widget.TabLayout; import android.support.v4.view.PagerAdapter; import android.support.v4.view.ViewPager; import android.support.v7.app.AppCompatActivity; import android.support.v7.widget.Toolbar; import android.view.View; import android.widget.ImageButton; import android.widget.TextView; import android.widget.Toast;
import com.zaid.recyclerviewsqlite.R;
public class My_Notes_View_Main extends AppCompatActivity implements View.OnClickListener {
private final int numOfPages = 3;
private final String[] pageTitle = {"Definition", "Syntax", "Code"};
private ImageButton view;
private TextView content;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.my_notes_view_main);
view = (ImageButton)findViewById(R.id.view);
content = (TextView)findViewById(R.id.textView);
view();
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar1);
setSupportActionBar(toolbar);
TabLayout tabLayout = (TabLayout) findViewById(R.id.tab_layout);
for (int i = 0; i < numOfPages; i++) {
tabLayout.addTab(tabLayout.newTab().setText(pageTitle[i]));
}
//set gravity for tab bar
tabLayout.setTabGravity(TabLayout.GRAVITY_FILL);
final ViewPager viewPager = (ViewPager) findViewById(R.id.pager);
final PagerAdapter adapter = new My_Notes_View_MyPagerAdapter(getSupportFragmentManager(), numOfPages);
viewPager.setAdapter(adapter);
viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
tabLayout.setOnTabSelectedListener(onTabSelectedListener(viewPager));
}
private TabLayout.OnTabSelectedListener onTabSelectedListener(final ViewPager pager) {
return new TabLayout.OnTabSelectedListener() {
@Override
public void onTabSelected(TabLayout.Tab tab) {
pager.setCurrentItem(tab.getPosition());
/**
if(tab.getPosition() == 1){
content.setText(getIntent().getStringExtra("note_def"));
} else if (tab.getPosition() == 2) {
content.setText(getIntent().getStringExtra("note_syntax"));
} else if (tab.getPosition() == 3) {
content.setText(getIntent().getStringExtra("note_code"));
}
*/
}
@Override
public void onTabUnselected(TabLayout.Tab tab) {
}
@Override
public void onTabReselected(TabLayout.Tab tab) {
}
};
}
/** @Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.my_notes_add_main_menu, menu);
return true;
} */
public void view(){
view.setOnClickListener(new View.OnClickListener() {
@Override public void onClick(View v) {
// TODO Auto-generated method stub
Toast.makeText(getApplicationContext(), "Add Click", Toast.LENGTH_SHORT).show(); }
});
}
@Override public void onClick(View v) { // TODO Auto-generated method stub
}
}
我的LogCat已经明确表示我在onTabSelectedListener（）第63行中有一个nullPointerException但我不知道如何解决这个问题。
这是我的LogCat
03-18 12:25:39.582: E/InputEventReceiver(16326): Exception dispatching input event.
03-18 12:25:39.582: E/MessageQueue-JNI(16326): Exception in MessageQueue callback: handleReceiveCallback
03-18 12:25:39.592: D/dalvikvm(16326): GC_FOR_ALLOC freed 242K, 8% free 3959K/4276K, paused 10ms, total 10ms
03-18 12:25:39.602: E/MessageQueue-JNI(16326): java.lang.NullPointerException
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at com.zaid.recyclerviewsqlite.viewNotes.My_Notes_View_Main$1.onTabSelected(My_Notes_View_Main.java:62)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.support.design.widget.TabLayout.selectTab(TabLayout.java:871)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.support.design.widget.TabLayout$TabLayoutOnPageChangeListener.onPageSelected(TabLayout.java:1759)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.support.v4.view.ViewPager.dispatchOnPageSelected(ViewPager.java:1794)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.support.v4.view.ViewPager.scrollToItem(ViewPager.java:569)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.support.v4.view.ViewPager.setCurrentItemInternal(ViewPager.java:553)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.support.v4.view.ViewPager.onTouchEvent(ViewPager.java:2102)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.view.View.dispatchTouchEvent(View.java:7711)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2210)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1945)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2216)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1959)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2216)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1959)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2216)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1959)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2216)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1959)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2216)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1959)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2216)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1959)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2216)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1959)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:2068)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1515)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.app.Activity.dispatchTouchEvent(Activity.java:2458)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.support.v7.view.WindowCallbackWrapper.dispatchTouchEvent(WindowCallbackWrapper.java:60)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.support.v7.view.WindowCallbackWrapper.dispatchTouchEvent(WindowCallbackWrapper.java:60)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:2016)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.view.View.dispatchPointerEvent(View.java:7891)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.view.ViewRootImpl$ViewPostImeInputStage.processPointerEvent(ViewRootImpl.java:3954)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:3833)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3399)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3449)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3418)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:3525)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3426)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:3582)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3399)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3449)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3418)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3426)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3399)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:5602)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.view.ViewRootImpl.doProcessInputEvents(ViewRootImpl.java:5582)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:5553)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.view.ViewRootImpl$WindowInputEventReceiver.onInputEvent(ViewRootImpl.java:5682)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.view.InputEventReceiver.dispatchInputEvent(InputEventReceiver.java:185)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.os.MessageQueue.nativePollOnce(Native Method)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.os.MessageQueue.next(MessageQueue.java:138)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.os.Looper.loop(Looper.java:123)
03-18 12:25:39.602: E/MessageQueue-JNI(16326): at android.app.ActivityThread
03-18 12:25:39.602: D/AndroidRuntime(16326): Shutting down VM
答案 0 :(得分：0)
如果@+id/textView不在my_notes_view_main.xml
然后content为空。
content = (TextView)findViewById(R.id.textView);
来自findViewById
查找由
onCreate(Bundle)中处理的XML中的id属性标识的视图。返回 - 找到的视图或 null否则
由于您提到该视图是Fragment布局的一部分，因此它为null，并且您将获得NullPointerException。