我是使用Android编程和网络的菜鸟，当我设置一个TextView的文本时，我不明白我的应用程序崩溃的原因。
我的第一个Activity是一个问题：
public class MainActivity extends ActionBarActivity {
private static Spinner spinner;
private static LinkedList<Integer> list;
private static EditText editText1, editText2;
private RadioGroup rG;
public ArrayList<String> info;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment()).commit();
}
}
private static void ageSpinner(View v) {
list = new LinkedList<Integer>();
for (Integer i = 0; i <= 110; i++) {
list.add(i);
}
ArrayAdapter<Integer> spinnerAdapter = new ArrayAdapter<Integer>(
v.getContext(), android.R.layout.simple_spinner_item, list);
spinnerAdapter
.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spinner.setAdapter(spinnerAdapter);
}
public void goResult(View v) {
info = new ArrayList<String>();
editText1 = (EditText) findViewById(R.id.editText1);
editText2 = (EditText) findViewById(R.id.editText2);
info.add(editText1.getText().toString());
info.add(editText2.getText().toString());
rG = (RadioGroup) findViewById(R.id.radioGroup1);
int select = rG.getCheckedRadioButtonId();
if (select == R.id.radio0) {
info.add("Male");
} else {
info.add("Female");
}
info.add(spinner.getSelectedItem().toString());
Intent i = new Intent(this, Result.class);
i.putExtra("miki", info);
startActivity(i);
}
@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();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
public PlaceholderFragment() {
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container,
false);
spinner = (Spinner) rootView.findViewById(R.id.spinner1);
ageSpinner(rootView);
return rootView;
}
}
}
其他类是我从过去的活动中传递的打印结果;
public class Result extends ActionBarActivity {
private TextView nombre;
private TextView edad;
private TextView sex;
private List<String> infos;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_result);
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment()).commit();
}
getResult();
}
public void getResult (){
Bundle b = this.getIntent().getExtras();
infos = new ArrayList<String>();
nombre = (TextView) findViewById(R.id.textView2);
edad = (TextView) findViewById(R.id.textView4);
sex = (TextView) findViewById(R.id.textView6);
infos = b.getStringArrayList("miki");
nombre.setText(infos.get(1).toString() + " " + infos.get(0).toString());
edad.setText(infos.get(2).toString());
sex.setText(infos.get(3).toString());
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.result, 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();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
public PlaceholderFragment() {
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_result,
container, false);
return rootView;
}
}
}
这是de logcat：
05-12 05:11:04.855: E/AndroidRuntime(1357): FATAL EXCEPTION: main
05-12 05:11:04.855: E/AndroidRuntime(1357): Process: com.example.lab_1, PID: 1357
05-12 05:11:04.855: E/AndroidRuntime(1357): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.lab_1/com.example.lab_1.Result}: java.lang.NullPointerException
05-12 05:11:04.855: E/AndroidRuntime(1357): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
05-12 05:11:04.855: E/AndroidRuntime(1357): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
05-12 05:11:04.855: E/AndroidRuntime(1357): at android.app.ActivityThread.access$800(ActivityThread.java:135)
05-12 05:11:04.855: E/AndroidRuntime(1357): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
05-12 05:11:04.855: E/AndroidRuntime(1357): at android.os.Handler.dispatchMessage(Handler.java:102)
05-12 05:11:04.855: E/AndroidRuntime(1357): at android.os.Looper.loop(Looper.java:136)
05-12 05:11:04.855: E/AndroidRuntime(1357): at android.app.ActivityThread.main(ActivityThread.java:5017)
05-12 05:11:04.855: E/AndroidRuntime(1357): at java.lang.reflect.Method.invokeNative(Native Method)
05-12 05:11:04.855: E/AndroidRuntime(1357): at java.lang.reflect.Method.invoke(Method.java:515)
05-12 05:11:04.855: E/AndroidRuntime(1357): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
05-12 05:11:04.855: E/AndroidRuntime(1357): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
05-12 05:11:04.855: E/AndroidRuntime(1357): at dalvik.system.NativeStart.main(Native Method)
05-12 05:11:04.855: E/AndroidRuntime(1357): Caused by: java.lang.NullPointerException
05-12 05:11:04.855: E/AndroidRuntime(1357): at com.example.lab_1.Result.getResult(Result.java:53)
05-12 05:11:04.855: E/AndroidRuntime(1357): at com.example.lab_1.Result.onCreate(Result.java:36)
05-12 05:11:04.855: E/AndroidRuntime(1357): at android.app.Activity.performCreate(Activity.java:5231)
05-12 05:11:04.855: E/AndroidRuntime(1357): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
05-12 05:11:04.855: E/AndroidRuntime(1357): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
05-12 05:11:04.855: E/AndroidRuntime(1357): ... 11 more
有什么想法吗？
谢谢!!
答案 0 :(得分：1)
首先在MainActivity ArrayList<String> Intent中添加Intent i = new Intent(this, Result.class);
i.putStringArrayListExtra("miki", info);
startActivity(i);
，如下所示：
Result在getResult();活动中，在if (savedInstanceState == null) {条件之前调用@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_result);
getResult();
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment()).commit();
}
}
方法，如下所示：
{{1}}
答案 1 :(得分：0)
NullPointerException中有一个getResult（可能是因为findViewById的所有来电都在返回Null）
您可能已在片段XML中声明了UI组件（TextView等）并尝试从R.layout.activity_result检索它，反之亦然。检查您是否在R.layout.fragment_main中声明了UI组件，并从onCreateView检索它们。
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_result,
container, false);
nombre = (TextView) rootView.findViewById(R.id.textView2);
edad = (TextView) rootView.findViewById(R.id.textView4);
sex = (TextView) rootView.findViewById(R.id.textView6);
return rootView;
}