我学习android studio编程,我的程序有问题, 当我想使用intent语句进入新活动我的应用程序崩溃了, 这是我的主要活动;
public class MainActivity extends AppCompatActivity {
private FirebaseAuth mAuth;
private FirebaseAuth.AuthStateListener mAuthListener;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mAuth = FirebaseAuth.getInstance();
}
public void onStart(){
super.onStart();
FirebaseUser CurrentUser = mAuth.getCurrentUser();
if(CurrentUser == null){
Intent StartIntent = new Intent(MainActivity.this,
StartActivity.class);
startActivity(StartIntent);
finish();
}
}
}
这很明显:
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:supportsRtl="true"
android:theme="@style/AppTheme">
<activity android:name=".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=".StartActivity"
android:label="@string/app_name">
</activity>
没有错误消息 但这就是我在android监视器中所拥有的:
08-23 21:50:33.507 11264-11264/? E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.ruse.ayse.areyousmartenough, PID: 11264
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.ruse.ayse.areyousmartenough/com.ruse.ayse.areyousmartenough.StartActivity}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2327)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2378)
at android.app.ActivityThread.access$800(ActivityThread.java:155)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1244)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5433)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1268)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1084)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at com.ruse.ayse.areyousmartenough.StartActivity.onCreate(StartActivity.java:31)
at android.app.Activity.performCreate(Activity.java:5301)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1094)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2291)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2378)
at android.app.ActivityThread.access$800(ActivityThread.java:155)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1244)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5433)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1268)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1084)
at dalvik.system.NativeStart.main(Native Method)
我通过添加&#34; intent-filter&#34;将此问题解决到另一个项目中进入清单文件,但它不适用于这个项目,
这是StartActivity:
public class StartActivity extends AppCompatActivity {
private Button mRegBtn ;
private Button mLoginBtn;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_start);
mRegBtn = (Button) findViewById(R.id.RegBtn);
mLoginBtn = (Button) findViewById(R.id.LoginBtn);
mRegBtn.setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View view) {
Intent createAccount = new Intent(StartActivity.this, RegisterActivity.class);
startActivity(createAccount);
}
});
mLoginBtn.setOnClickListener(new View.OnClickListener(){ /////this is line 31
@Override
public void onClick(View view) {
Intent loginAccount = new Intent(StartActivity.this, LoginActivity.class);
startActivity(loginAccount);
}
});
}}
答案 0 :(得分:2)
你的问题出在StartActivity.java:31,你试图从空引用中读取。
根据您的评论,您希望错过从Layout =
获取mLoginBtnmLoginBtn = (Button) findViewById(R.id.btn_login);