Question

当执行我的onClick方法按钮以显示来自editText的文本时，我的应用程序由于NullPointerException而崩溃，我无法弄清楚原因。当我完全删除对editText的引用时，一切正常。我做错了什么？

public void onClick(View v) {
    EditText editText1 = (EditText) v.findViewById (R.id.editText1);

    switch (v.getId()) {       
    //add entry to the List
        case R.id.button1:

            Toast.makeText(getActivity(), "Clicked on add button" + " CRN: " + editText1.getText().toString(), Toast.LENGTH_LONG).show();

        case R.id.button2:
            Toast.makeText(getActivity(), "Clicked on delete button", Toast.LENGTH_LONG).show();


    }
   }

有问题的错误：

01-12 19:32:57.726: E/AndroidRuntime(23216): FATAL EXCEPTION: main
01-12 19:32:57.726: E/AndroidRuntime(23216): java.lang.NullPointerException
01-12 19:32:57.726: E/AndroidRuntime(23216):    at com.example.project.ClassesFragment.onClick(ClassesFragment.java:85)
01-12 19:32:57.726: E/AndroidRuntime(23216):    at android.view.View.performClick(View.java:4475)
01-12 19:32:57.726: E/AndroidRuntime(23216):    at android.view.View$PerformClick.run(View.java:18786)
01-12 19:32:57.726: E/AndroidRuntime(23216):    at android.os.Handler.handleCallback(Handler.java:730)
01-12 19:32:57.726: E/AndroidRuntime(23216):    at android.os.Handler.dispatchMessage(Handler.java:92)
01-12 19:32:57.726: E/AndroidRuntime(23216):    at android.os.Looper.loop(Looper.java:137)
01-12 19:32:57.726: E/AndroidRuntime(23216):    at android.app.ActivityThread.main(ActivityThread.java:5419)
01-12 19:32:57.726: E/AndroidRuntime(23216):    at java.lang.reflect.Method.invokeNative(Native Method)
01-12 19:32:57.726: E/AndroidRuntime(23216):    at java.lang.reflect.Method.invoke(Method.java:525)
01-12 19:32:57.726: E/AndroidRuntime(23216):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1187)
01-12 19:32:57.726: E/AndroidRuntime(23216):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1003)
01-12 19:32:57.726: E/AndroidRuntime(23216):    at de.robv.android.xposed.XposedBridge.main(XposedBridge.java:115)
01-12 19:32:57.726: E/AndroidRuntime(23216):    at dalvik.system.NativeStart.main(Native Method)
01-12 19:33:12.040: I/Process(23216): Sending signal. PID: 23216 SIG: 9

Answer 1

如果是片段布局，则在onCreateView

 EditText ediText1;
 @Override
 public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    // TODO Auto-generated method stub
     View v = inflater.inflate(R.layout.fragmentlayout, container, false);
              editText1 = (EditText) v.findViewById (R.id.editText1);
    return v;
}

或

您可能引用了错误的ID。

你错过了休息

case R.id.button1:

        Toast.makeText(getActivity(), "Clicked on add button" + " CRN: " + editText1.getText().toString(), Toast.LENGTH_LONG).show();

break; // missing

Answer 2

public void onClick(View v) {
//defining edit text
EditText editText1 = (EditText) findViewById (R.id.editText1);

switch (v.getId()) {       
//add entry to the List
    case R.id.button1:
        Toast.makeText(getActivity(), "Clicked on add button" + " CRN: " + editText1.getText().toString(), Toast.LENGTH_LONG).show();
        //stop button event
        break;
    case R.id.button2:
        Toast.makeText(getActivity(), "Clicked on delete button", Toast.LENGTH_LONG).show();
        //stop button event
        break;

}
}

从editText获取文本时onClick崩溃

2 个答案: