Question

我有多个按钮应该将不同的字符串值传递给单个活动。当我尝试在我的主要活动中包含按钮监听器时，我得到了NullPointer异常，当我尝试stackoverflow中的每个帖子时，这就是杀了我，它应该可以工作！我无法弄清楚我的问题是什么。这是一些代码：

fragment_layout中的按钮定义：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/LinearLayout1"
style="@style/AppBaseTheme"
android:screenOrientation="portrait"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity=""
android:animateLayoutChanges="true"
android:background="#f000"
android:baselineAligned="false"
android:gravity="top"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
tools:context=".MainActivity" >

<LinearLayout
    android:id="@+id/LinearLayout01"
    style="@style/lineralLayout"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_weight="1"
    android:gravity="top"
    android:orientation="vertical"
    android:weightSum="3" >

  <Button
    android:id="@+id/button1s"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:background="@drawable/f0"
    android:layout_weight="1"
     />

  <Button
    android:id="@+id/button2s"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:background="@drawable/f2"
    android:layout_weight="1"
     />

 <Button
    android:id="@+id/button3"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:background="@drawable/f8"
    android:layout_weight="1" />

 <Button
    android:id="@+id/button4"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:background="@drawable/f40"
    android:layout_weight="1" />

 <Button
     android:id="@+id/button5"
     android:layout_width="wrap_content"
     android:layout_height="wrap_content"
     android:background="@drawable/dont_know"
     android:layout_weight="1" />

</LinearLayout>
</LinearLayout>

MainActivity的代码：

public class MainActivity extends Activity implements View.OnClickListener {
private Button button1;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    button1 = (Button) findViewById(R.id.button1s);
    button1.setOnClickListener(this);
    button2 = (Button) findViewById(R.id.button2s);
    button2.setOnClickListener(this);
}

@Override
public void onClick(View v) {
    String toParse = new String();
    switch (v.getId()) {
    case R.id.button1s:
        toParse = "0";
        break;
    case R.id.button2s:
        toParse = "90";
        break;

    }
    Intent intent = new Intent(MainActivity.this, DuzaKartaActivity.class);
    intent.putExtra(TEXT_KEY, toParse);
    startActivity(intent);

}

Fragment Class中的代码：

public class StandardFragment extends Fragment {

public StandardFragment(){}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {

    View rootView = inflater.inflate(R.layout.fragment_layout, container, false);
    return rootView;
}

}

logcat输出：

10-12 11:14:28.499: E/AndroidRuntime(3265): FATAL EXCEPTION: main
10-12 11:14:28.499: E/AndroidRuntime(3265): Process: com.ericpol.scrumpoker, PID: 3265
10-12 11:14:28.499: E/AndroidRuntime(3265): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.ericpol.scrumpoker/com.ericpol.scrumpoker.MainActivity}: java.lang.NullPointerException
10-12 11:14:28.499: E/AndroidRuntime(3265):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
10-12 11:14:28.499: E/AndroidRuntime(3265):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
10-12 11:14:28.499: E/AndroidRuntime(3265):     at android.app.ActivityThread.access$800(ActivityThread.java:135)
10-12 11:14:28.499: E/AndroidRuntime(3265):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
10-12 11:14:28.499: E/AndroidRuntime(3265):     at android.os.Handler.dispatchMessage(Handler.java:102)
10-12 11:14:28.499: E/AndroidRuntime(3265):     at android.os.Looper.loop(Looper.java:136)
10-12 11:14:28.499: E/AndroidRuntime(3265):     at android.app.ActivityThread.main(ActivityThread.java:5017)
10-12 11:14:28.499: E/AndroidRuntime(3265):     at java.lang.reflect.Method.invokeNative(Native Method)
10-12 11:14:28.499: E/AndroidRuntime(3265):     at java.lang.reflect.Method.invoke(Method.java:515)
10-12 11:14:28.499: E/AndroidRuntime(3265):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
10-12 11:14:28.499: E/AndroidRuntime(3265):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
10-12 11:14:28.499: E/AndroidRuntime(3265):     at dalvik.system.NativeStart.main(Native Method)
10-12 11:14:28.499: E/AndroidRuntime(3265): Caused by: java.lang.NullPointerException
10-12 11:14:28.499: E/AndroidRuntime(3265):     at com.ericpol.scrumpoker.MainActivity.onCreate(MainActivity.java:80)
10-12 11:14:28.499: E/AndroidRuntime(3265):     at android.app.Activity.performCreate(Activity.java:5231)
10-12 11:14:28.499: E/AndroidRuntime(3265):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
10-12 11:14:28.499: E/AndroidRuntime(3265):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)

Answer 1

你应该改变这个

setContentView(R.layout.activity_main);

到

setContentView(R.layout.fragment_layout);

Answer 2

您的Button是在fragment_layout内定义的，您正试图让活动膨胀，然后find the view。这不行。您必须inflate fragment_layout和致电findViewById

或

创建一个扩展Fragment的类并覆盖onCreateView方法并使用FragmentManager将片段添加到活动中。在覆盖onCreateView方法中，您可以设置侦听器

Answer 3

我找不到问题所在，所以我在fragemt_layout xml中设置了onClick方法，并从MainActivity中删除了onClick监听器。

按钮监听器与碎片

3 个答案: