由于某些原因,每次我尝试启动我的应用程序时都会收到以下错误:
我检查了我的清单文件,每个活动都已添加。
我在启动应用程序时仅使用一种方法:
Unable to instantiate activity ComponentInfo{com.example.lifeahead/com.example.lifeahead.MainActivity}:java.lang.NullPointerException
我检查了我的清单文件,每个活动都已添加。
我在启动应用程序时仅使用一种方法:
private void logIn(){
Button logIn = (Button) findViewById(R.id.login);
logIn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
Intent loginIntent = new Intent(MainActivity.this, HomeActivity.class);
loginIntent.putExtra("cmUN", cmUN);
loginIntent.putExtra("cmPW", cmPW);
startActivity(loginIntent);
}
});
}
这是onCreate函数:
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();
}
logIn();
}
完整日志:
E
/AndroidRuntime(1607): FATAL EXCEPTION: main
E/AndroidRuntime(1607): Process: com.example.lifeahead, PID: 1607
E/AndroidRuntime(1607): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.lifeahead/com.example.lifeahead.MainActivity}: java.lang.NullPointerException
E/AndroidRuntime(1607): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2121)
E/AndroidRuntime(1607): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
E/AndroidRuntime(1607): at android.app.ActivityThread.access$800(ActivityThread.java:135)
E/AndroidRuntime(1607): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
E/AndroidRuntime(1607): at android.os.Handler.dispatchMessage(Handler.java:102)
E/AndroidRuntime(1607): at android.os.Looper.loop(Looper.java:136)
E/AndroidRuntime(1607): at android.app.ActivityThread.main(ActivityThread.java:5017)
E/AndroidRuntime(1607): at java.lang.reflect.Method.invokeNative(Native Method)
E/AndroidRuntime(1607): at java.lang.reflect.Method.invoke(Method.java:515)
E/AndroidRuntime(1607): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
E/AndroidRuntime(1607): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
E/AndroidRuntime(1607): at dalvik.system.NativeStart.main(Native Method)
E/AndroidRuntime(1607): Caused by: java.lang.NullPointerException
E/AndroidRuntime(1607): at android.app.Activity.findViewById(Activity.java:1884)
E/AndroidRuntime(1607): at com.example.lifeahead.MainActivity.<init>(MainActivity.java:22)
E/AndroidRuntime(1607): at java.lang.Class.newInstanceImpl(Native Method)
E/AndroidRuntime(1607): at java.lang.Class.newInstance(Class.java:1208)
E/AndroidRuntime(1607): at android.app.Instrumentation.newActivity(Instrumentation.java:1061)
E/AndroidRuntime(1607): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2112)
E/AndroidRuntime(1607): ... 11 more
我感激所有能够提供帮助的人!