从启动画面切换到 MainActivity 时应用程序崩溃
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【中文标题】从启动画面切换到 MainActivity 时应用程序崩溃【英文标题】：App Crashes When Switching from Splash Screen to MainActivity 【发布时间】：2016-03-04 20:45:07 【问题描述】：所以，我每次尝试运行我的应用程序时都会收到此错误，它会启动并在正确的时间内启动 SplashActivity，然后尝试启动 MainActivity 并立即失败。
据我所知，这是一个 NullPointer 错误，但我终生无法弄清楚是什么。
错误：
11-30 21:03:33.146 3216-3216/? D/dalvikvm: Not late-enabling CheckJNI (already on)
11-30 21:03:34.646 3216-3216/edu.wmich.lab4aoneill3193 W/dalvikvm: VFY: unable to find class referenced in signature (Landroid/view/SearchEvent;)
11-30 21:03:34.646 3216-3216/edu.wmich.lab4aoneill3193 I/dalvikvm: Could not find method android.view.Window$Callback.onSearchRequested, referenced from method android.support.v7.view.WindowCallbackWrapper.onSearchRequested
11-30 21:03:34.656 3216-3216/edu.wmich.lab4aoneill3193 W/dalvikvm: VFY: unable to resolve interface method 14517: Landroid/view/Window$Callback;.onSearchRequested (Landroid/view/SearchEvent;)Z
11-30 21:03:34.656 3216-3216/edu.wmich.lab4aoneill3193 D/dalvikvm: VFY: replacing opcode 0x72 at 0x0002
11-30 21:03:34.656 3216-3216/edu.wmich.lab4aoneill3193 I/dalvikvm: Could not find method android.view.Window$Callback.onWindowStartingActionMode, referenced from method android.support.v7.view.WindowCallbackWrapper.onWindowStartingActionMode
11-30 21:03:34.656 3216-3216/edu.wmich.lab4aoneill3193 W/dalvikvm: VFY: unable to resolve interface method 14521: Landroid/view/Window$Callback;.onWindowStartingActionMode (Landroid/view/ActionMode$Callback;I)Landroid/view/ActionMode;
11-30 21:03:34.656 3216-3216/edu.wmich.lab4aoneill3193 D/dalvikvm: VFY: replacing opcode 0x72 at 0x0002
11-30 21:03:34.856 3216-3216/edu.wmich.lab4aoneill3193 D/dalvikvm: GC_FOR_ALLOC freed 129K, 7% free 2772K/2972K, paused 57ms, total 59ms
11-30 21:03:34.856 3216-3216/edu.wmich.lab4aoneill3193 I/dalvikvm-heap: Grow heap (frag case) to 5.308MB for 2658320-byte allocation
11-30 21:03:34.916 3216-3225/edu.wmich.lab4aoneill3193 D/dalvikvm: GC_FOR_ALLOC freed <1K, 4% free 5367K/5572K, paused 48ms, total 48ms
11-30 21:03:35.646 3216-3216/edu.wmich.lab4aoneill3193 I/dalvikvm: Could not find method android.content.res.TypedArray.getChangingConfigurations, referenced from method android.support.v7.widget.TintTypedArray.getChangingConfigurations
11-30 21:03:35.646 3216-3216/edu.wmich.lab4aoneill3193 W/dalvikvm: VFY: unable to resolve virtual method 409: Landroid/content/res/TypedArray;.getChangingConfigurations ()I
11-30 21:03:35.646 3216-3216/edu.wmich.lab4aoneill3193 D/dalvikvm: VFY: replacing opcode 0x6e at 0x0002
11-30 21:03:35.656 3216-3216/edu.wmich.lab4aoneill3193 I/dalvikvm: Could not find method android.content.res.TypedArray.getType, referenced from method android.support.v7.widget.TintTypedArray.getType
11-30 21:03:35.656 3216-3216/edu.wmich.lab4aoneill3193 W/dalvikvm: VFY: unable to resolve virtual method 431: Landroid/content/res/TypedArray;.getType (I)I
11-30 21:03:35.656 3216-3216/edu.wmich.lab4aoneill3193 D/dalvikvm: VFY: replacing opcode 0x6e at 0x0002
11-30 21:03:35.866 3216-3216/edu.wmich.lab4aoneill3193 W/EGL_emulation: eglSurfaceAttrib not implemented
11-30 21:03:35.886 3216-3216/edu.wmich.lab4aoneill3193 D/OpenGLRenderer: Enabling debug mode 0
11-30 21:03:41.596 3216-3216/edu.wmich.lab4aoneill3193 D/AndroidRuntime: Shutting down VM
11-30 21:03:41.596 3216-3216/edu.wmich.lab4aoneill3193 W/dalvikvm: threadid=1: thread exiting with uncaught exception (group=0xb3ac0ba8)
11-30 21:03:41.666 3216-3216/edu.wmich.lab4aoneill3193 E/AndroidRuntime: FATAL EXCEPTION: main
Process: edu.wmich.lab4aoneill3193, PID: 3216
java.lang.RuntimeException: Unable to instantiate activity ComponentInfoedu.wmich.lab4aoneill3193/edu.wmich.lab4aoneill3193.MainActivity: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2121)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
at android.app.ActivityThread.access$800(ActivityThread.java:135)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5017)
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:779)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at android.app.Activity.findViewById(Activity.java:1884)
at edu.wmich.lab4aoneill3193.MainActivity.<init>(MainActivity.java:36)
at java.lang.Class.newInstanceImpl(Native Method)
at java.lang.Class.newInstance(Class.java:1208)
at android.app.Instrumentation.newActivity(Instrumentation.java:1061)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2112)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
at android.app.ActivityThread.access$800(ActivityThread.java:135)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5017)
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:779)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
at dalvik.system.NativeStart.main(Native Method)
11-30 21:08:42.916 3216-3216/edu.wmich.lab4aoneill3193 I/Process: Sending signal. PID: 3216 SIG: 9
Android 清单：
<?xml version="1.0" encoding="utf-8"?>
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:supportsRtl="true"
android:theme="@style/AppTheme">
<activity android:name=".SplashActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".MainActivity"></activity>
</application>
SplashActivity.java：
package edu.wmich.lab4aoneill3193;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import java.util.Timer;
import java.util.TimerTask;
public class SplashActivity extends AppCompatActivity
@Override
protected void onCreate(Bundle savedInstanceState)
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_splash);
TimerTask splash = new TimerTask()
@Override
public void run()
finish();
startActivity(new Intent(SplashActivity.this,MainActivity.class));
;
Timer opening = new Timer();
opening.schedule(splash,5000);
MainActivity.Java：
package edu.wmich.lab4aoneill3193
import android.app.DatePickerDialog;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.DatePicker;
import android.widget.RadioButton;
import android.widget.TextView;
import android.widget.Toast;
import java.text.DateFormat;
import java.util.Calendar;
public class MainActivity extends AppCompatActivity
private TextView reservation;
final RadioButton chcOne = (RadioButton) findViewById(R.id.choiceOne);
final RadioButton chcTwo = (RadioButton) findViewById(R.id.choiceTwo);
final RadioButton chcThree = (RadioButton) findViewById(R.id.choiceThree);
@Override
protected void onCreate(Bundle savedInstanceState)
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
reservation = (TextView) findViewById(R.id.rsltText);
Button btnDate = (Button) findViewById(R.id.btnDate);
btnDate.setOnClickListener(new View.OnClickListener()
@Override
public void onClick(View v)
new DatePickerDialog(MainActivity.this, date, cal.get(Calendar.YEAR),
cal.get(Calendar.MONTH), cal.get(Calendar.DAY_OF_MONTH)).show();
);
Calendar cal = Calendar.getInstance();
DateFormat fmtDate = DateFormat.getDateInstance();
DatePickerDialog.OnDateSetListener date = new DatePickerDialog.OnDateSetListener()
@Override
public void onDateSet(DatePicker view, int year, int monthOfYear, int dayOfMonth)
cal.set(Calendar.YEAR, year);
cal.set(Calendar.MONTH, monthOfYear);
cal.set(Calendar.DAY_OF_MONTH, dayOfMonth);
if (chcOne.isChecked())
reservation.setText("A Massive Asteroid Will Impact The Earth on "
+ fmtDate.format(cal.getTime()));
else Toast.makeText(MainActivity.this, "Choose Something!",Toast.LENGTH_LONG).show();
if (chcTwo.isChecked())
reservation.setText("Massive Tsunamis Will Engulf The World on "
+ fmtDate.format(cal.getTime()));
else Toast.makeText(MainActivity.this, "Choose Something!",Toast.LENGTH_LONG).show();
if (chcThree.isChecked())
reservation.setText("A Fatal Disease Will OverWhelm The World on "
+ fmtDate.format(cal.getTime()));
else Toast.makeText(MainActivity.this, "Choose Something!",Toast.LENGTH_LONG).show();
;
【问题讨论】：
【参考方案1】：findViewById(int) 只能在setContentView(int) 设置活动布局后调用。如果你膨胀你的视图，那么你可以在那个视图对象上调用findViewById(int)。
所以把你的代码改成
MainActivity.Java： 公共类 MainActivity 扩展 AppCompatActivity
private TextView reservation;
RadioButton chcOne;
RadioButton chcTwo;
RadioButton chcThree;
@Override
protected void onCreate(Bundle savedInstanceState)
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
reservation = (TextView) findViewById(R.id.rsltText);
Button btnDate = (Button) findViewById(R.id.btnDate);
chcOne = (RadioButton) findViewById(R.id.choiceOne);
chcTwo = (RadioButton) findViewById(R.id.choiceTwo);
chcThree = (RadioButton) findViewById(R.id.choiceThree);
btnDate.setOnClickListener(new View.OnClickListener()
@Override
public void onClick(View v)
new DatePickerDialog(MainActivity.this, date, cal.get(Calendar.YEAR),
cal.get(Calendar.MONTH), cal.get(Calendar.DAY_OF_MONTH)).show();
);
Calendar cal = Calendar.getInstance();
DateFormat fmtDate = DateFormat.getDateInstance();
DatePickerDialog.OnDateSetListener date = new DatePickerDialog.OnDateSetListener()
@Override
public void onDateSet(DatePicker view, int year, int monthOfYear, int dayOfMonth)
cal.set(Calendar.YEAR, year);
cal.set(Calendar.MONTH, monthOfYear);
cal.set(Calendar.DAY_OF_MONTH, dayOfMonth);
if (chcOne.isChecked())
reservation.setText("A Massive Asteroid Will Impact The Earth on "
+ fmtDate.format(cal.getTime()));
else Toast.makeText(MainActivity.this, "Choose Something!",Toast.LENGTH_LONG).show();
if (chcTwo.isChecked())
reservation.setText("Massive Tsunamis Will Engulf The World on "
+ fmtDate.format(cal.getTime()));
else Toast.makeText(MainActivity.this, "Choose Something!",Toast.LENGTH_LONG).show();
if (chcThree.isChecked())
reservation.setText("A Fatal Disease Will OverWhelm The World on "
+ fmtDate.format(cal.getTime()));
else Toast.makeText(MainActivity.this, "Choose Something!",Toast.LENGTH_LONG).show();
;
希望对你有帮助...
【讨论】：
【参考方案2】：您好，您在开始下一项活动后先完成您的活动，尝试改变这种方式，
TimerTask splash = new TimerTask()
@Override
public void run()
startActivity(new Intent(SplashActivity.this,MainActivity.class));
finish();
;
Timer opening = new Timer();
opening.schedule(splash,5000);
【讨论】：
【参考方案3】：尝试直接在模拟器中打开 Main Activity，如果它正在运行，然后在 splash 中尝试这个
Thread timer= new Thread ()
public void run()
trysleep(2000);catch (InteruptedException e) e.printstacktrace() ;
finally Intent intent=new Intent(splash.this, MainActivity.class) startActivity(intent) ;
;
timer.start();
@Override
public void onPause()
super.onPause() ;
finish() ;
【讨论】：
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