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無論何時單擊按鈕啓動下一個活動，我都會收到以下錯誤。該應用程序假設啓動用戶可以通過API創建帳戶並將數據存儲到SQL Server的活動。致命例外：主要 - 啓動另一活動時
下面是錯誤：
致命異常：主要了java.lang.RuntimeException：無法啓動 活動 ComponentInfo {com.durban.labapp_unisa/com.durban.labapp_unisa.CreateUserActivity}： 的java .lang.NullPointerException在 android.app.ActivityThread.performLaunchActivity（ActivityThread.java:2180） 在 android.app.ActivityThread.handleLaunchActivity（ActivityThread.java:2230） 在android.app.ActivityThread.access $ 600（ActivityThread。 java：141） at android.app.ActivityThread $ H.handleMessage（ActivityThread.java:1234） at android.os.Handler.dispatchMessage（Handler.java:99）at android.os.Looper.loop（Looper.java:137）at android.app.ActivityThread.main（ActivityThread.java:5041）at java.lang.reflect.Method.invokeNative（Native Method）at java.lang.reflect.Method.invoke（Method.java:511）at com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:793） at com.android.internal.os.ZygoteInit.main（ZygoteInit.java:560）at dalvik.system.NativeStart.main（本地方法）由： java.lang.NullPointerException在 com.durban.labapp_unisa.CreateUserActivity.onCreate（CreateUserActivit y.java:44） 在android.app.Activity.performCreate（Activity.java:5104）在 android.app.Instrumentation.callActivityOnCreate（Instrumentation.java:1080） 在 android.app.ActivityThread.performLaunchActivity（ActivityThread的.java：2144） ...... 11多個
我的主要活動是：
public class MainActivity extends Activity implements OnClickListener {
Button btnLogin, btnRegister, btnDisplay;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//Initialize the layout components
btnLogin = (Button) findViewById(R.id.btnLogin);
btnRegister = (Button) findViewById(R.id.btnRegister);
//set onClick listeners for buttons
btnLogin.setOnClickListener(this);
btnRegister.setOnClickListener(this);
}
@Override
public void onClick(View v) {
switch(v.getId()){
case R.id.btnRegister:
Intent cr = new Intent(getApplicationContext(), CreateUserActivity.class);
startActivity(cr);
break;
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}
而另一項活動是：
/*
* This activity used to create users.
* When user is created it will redirect to LoginActivity.
*/
public class CreateUserActivity extends Activity {
EditText StudentNr, Surname, Fullname, Password,Cell, Qual;
Button Save, backButton;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_create_user);
// Show the Up button in the action bar.
setupActionBar();
//setup button listener
StudentNr = (EditText) findViewById(R.id.etStudentNr);
Surname = (EditText) findViewById(R.id.etSurname);
Fullname = (EditText) findViewById(R.id.etFullname);
Password = (EditText) findViewById(R.id.etPass1);
Cell = (EditText) findViewById(R.id.etCell);
Qual = (EditText) findViewById(R.id.etQua);
Save = (Button) findViewById(R.id.btnRegister);
backButton = (Button) findViewById(R.id.btnBack1);
Save.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
String studentNr, surname, fullname, password, cell, qual;
studentNr = StudentNr.getText().toString();
surname = Surname.getText().toString();
fullname = Fullname.getText().toString();
password = Password.getText().toString();
cell = Cell.getText().toString();
qual = Qual.getText().toString();
UserDetailsTable Records = new UserDetailsTable(studentNr,surname, fullname, password, cell, qual);
new AsyncCreateUser().execute(Records);
}
});
backButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
finish();
}
});
}
protected class AsyncCreateUser extends AsyncTask<UserDetailsTable, Void, Void>{
@Override
protected Void doInBackground(UserDetailsTable... params){
RestAPI api = new RestAPI();
try{
api.CreateNewAccount(params[0].getStudentNr(), params[1].getSurname(), params[2].getFullname(), params[3].getPassword(), params[4].getCellNr(), params[5].getQual());
}catch(Exception e){
Log.d("AsyncCreateUser", e.getMessage());
}
return null;
}
@Override
protected void onPostExecute(Void result){
//launch the login page after account successfully created
Intent i = new Intent(getApplicationContext(), MainActivity.class);
startActivity(i);
}
}
/**
* Set up the {@link android.app.ActionBar}, if the API is available.
*/
@TargetApi(Build.VERSION_CODES.HONEYCOMB)
private void setupActionBar() {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
getActionBar().setDisplayHomeAsUpEnabled(true);
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
// This ID represents the Home or Up button. In the case of this
// activity, the Up button is shown. Use NavUtils to allow users
// to navigate up one level in the application structure. For
// more details, see the Navigation pattern on Android Design:
//
// http://developer.android.com/design/patterns/navigation.html#up-vs-back
//
NavUtils.navigateUpFromSameTask(this);
return true;
}
return super.onOptionsItemSelected(item);
}
清單看起來像：
<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE"/>
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="17" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.durban.labapp_unisa.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="com.durban.labapp_unisa.CreateUserActivity"
android:label="@string/app_name"
android:launchMode="singleTop"
android:stateNotNeeded="true">
<intent-filter >
<action android:name="android.intent.action.CREATEUSERACTIVITY"/>
<action android:name="android.intent.category.DEFAULT"/>
</intent-filter>
</activity>
<activity
android:name="com.durban.labapp_unisa.JSONParser"
android:label="@string/app_name">
<intent-filter >
<action android:name="android.intent.action.JSONPARSER"/>
<action android:name="android.intent.category.DEFAULT"/>
</intent-filter>
</activity>
<activity
android:name="com.durban.labapp_unisa.RestAPI"
android:label="@string/app_name">
<intent-filter >
<action android:name="android.intent.action.RESTAPI"/>
<action android:name="android.intent.category.DEFAULT"/>
</intent-filter>
</activity>
<activity
android:name="com.durban.labapp_unisa.UserDetailsTable"
android:label="@string/app_name">
<intent-filter >
<action android:name="android.intent.action.USERDETAILSTABLE"/>
<action android:name="android.intent.category.DEFAULT"/>
</intent-filter>
</activity>
</application>
請幫助我這個
getApplicationContext（）到class name.this我認爲這是問題 –