Java 从初始屏幕切换到MainActivity时应用程序崩溃
因此，每次我尝试运行我的应用程序时，我都会遇到这个错误，它会启动并启动SplashActivity，持续正确的时间，然后尝试启动MainActivity，但立即失败 据我所知，这是一个空指针错误，但我一辈子也弄不清楚是什么 错误：Java 从初始屏幕切换到MainActivity时应用程序崩溃,java,android,android-activity,android-studio,crash,Java,Android,Android Activity,Android Studio,Crash,因此，每次我尝试运行我的应用程序时，我都会遇到这个错误，它会启动并启动SplashActivity，持续正确的时间，然后尝试启动MainActivity，但立即失败 据我所知，这是一个空指针错误，但我一辈子也弄不清楚是什么 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.lab4aoneill3
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 ComponentInfo{edu.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
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();
}
}
};
}
嗨，在你开始下一个活动后，你先完成你的活动，尝试以这种方式改变
TimerTask splash = new TimerTask() {
@Override
public void run() {
startActivity(new Intent(SplashActivity.this,MainActivity.class));
finish();
}
};
Timer opening = new Timer();
opening.schedule(splash,5000);
尝试在emulator中直接打开主活动（如果它正在运行），然后在splash中尝试此操作
Thread timer= new Thread () {
public void run() {
try{sleep(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() ;
}
findViewById（int）setContentView（int）findviewbyd（int）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();
}
}
};
}
TimerTask splash = new TimerTask() {
@Override
public void run() {
startActivity(new Intent(SplashActivity.this,MainActivity.class));
finish();
}
};
Timer opening = new Timer();
opening.schedule(splash,5000);
Thread timer= new Thread () {
public void run() {
try{sleep(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() ;
}
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();
}
}
};
}