Android 应用程序在启动时不断崩溃

Question

Android 应用程序在启动时不断崩溃。不过，我觉得一切都很好。

堆栈跟踪:

01-24 21:23:41.417: I/Process(767): Sending signal. PID: 767 SIG: 9
01-24 21:41:36.316: W/Trace(890): Unexpected value from nativeGetEnabledTags: 0
01-24 21:41:36.485: W/Trace(890): Unexpected value from nativeGetEnabledTags: 0
01-24 21:41:36.515: W/Trace(890): Unexpected value from nativeGetEnabledTags: 0
01-24 21:41:36.515: D/dalvikvm(890): newInstance failed: p0 i0 [0 a1
01-24 21:41:36.515: D/AndroidRuntime(890): Shutting down VM
01-24 21:41:36.515: W/dalvikvm(890): threadid=1: thread exiting with uncaught     exception (group=0x40a70930)
01-24 21:41:36.635: E/AndroidRuntime(890): FATAL EXCEPTION: main
01-24 21:41:36.635: E/AndroidRuntime(890): java.lang.RuntimeException: Unable to     instantiate activity ComponentInfo{com.example.bmisummative/com.example.bmisummative.MainActivity}:     java.lang.InstantiationException: can't instantiate class     com.example.bmisummative.MainActivity
01-24 21:41:36.635: E/AndroidRuntime(890):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2106)
01-24 21:41:36.635: E/AndroidRuntime(890):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
01-24 21:41:36.635: E/AndroidRuntime(890):  at android.app.ActivityThread.access$600(ActivityThread.java:141)
01-24 21:41:36.635: E/AndroidRuntime(890):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
01-24 21:41:36.635: E/AndroidRuntime(890):  at android.os.Handler.dispatchMessage(Handler.java:99)
01-24 21:41:36.635: E/AndroidRuntime(890):  at android.os.Looper.loop(Looper.java:137)
01-24 21:41:36.635: E/AndroidRuntime(890):  at android.app.ActivityThread.main(ActivityThread.java:5039)
01-24 21:41:36.635: E/AndroidRuntime(890):  at java.lang.reflect.Method.invokeNative(Native Method)
01-24 21:41:36.635: E/AndroidRuntime(890):  at java.lang.reflect.Method.invoke(Method.java:511)
01-24 21:41:36.635: E/AndroidRuntime(890):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
01-24 21:41:36.635: E/AndroidRuntime(890):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
01-24 21:41:36.635: E/AndroidRuntime(890):  at dalvik.system.NativeStart.main(Native Method)
01-24 21:41:36.635: E/AndroidRuntime(890): Caused by: java.lang.InstantiationException: can't instantiate class com.example.bmisummative.MainActivity
01-24 21:41:36.635: E/AndroidRuntime(890):  at java.lang.Class.newInstanceImpl(Native Method)
01-24 21:41:36.635: E/AndroidRuntime(890):  at java.lang.Class.newInstance(Class.java:1319)
01-24 21:41:36.635: E/AndroidRuntime(890):  at android.app.Instrumentation.newActivity(Instrumentation.java:1054)
01-24 21:41:36.635: E/AndroidRuntime(890):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2097)
01-24 21:41:36.635: E/AndroidRuntime(890):  ... 11 more
01-24 21:46:36.745: I/Process(890): Sending signal. PID: 890 SIG: 9

MainActivity 类:

package com.example.bmisummative;

import android.app.Activity;
import android.content.DialogInterface;
import android.view.View.OnClickListener;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public abstract class MainActivity extends Activity implements OnClickListener {
/** Called when the activity is first created. */
Button btn,btn1,btn2;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    btn = (Button) findViewById(R.id.buttonBMI);
    btn.setOnClickListener(this);
    btn1 = (Button) findViewById(R.id.buttonGain);
    btn1.setOnClickListener(this);
    btn2 = (Button) findViewById(R.id.buttonLoss);
    btn2.setOnClickListener(this);

}

@Override
public void onClick(View v) {
  if (v.getId() == R.id.buttonBMI) {
    startActivity(new Intent(this, MainActivity.class));
  }
  if (v.getId() == R.id.buttonGain) {
    startActivity(new Intent(this, weightgain.class));
  }
  if (v.getId() == R.id.buttonLoss) {
        startActivity(new Intent(this, weightgain.class));
      }

}

}

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    tools:context=".StartingPoint" 
    android:background="@drawable/grunge">

    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="Main Menu"
        android:textSize="45dp"
        android:layout_gravity="center"
        android:gravity="center" 
        android:textColor="#FFFFFF"
        android:id="@+id/tvDisplay"/>

    <Button
        android:id="@+id/buttonBMI"
        android:layout_width="250dp"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:text="BMI Calculator"
        android:textSize="20dp" />

    <Button
        android:id="@+id/buttonLoss"
        android:layout_width="250dp"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:text="Weight Loss Workouts"
        android:textSize="20dp" />

    <Button
        android:id="@+id/buttonGain"
        android:layout_width="250dp"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:text="Muscle Gain Workouts"
        android:textSize="20dp" />

</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.bmisummative"
    android:versionCode="1"
    android:versionName="1.0" >

    <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.example.bmisummative.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.example.bmiworking.calculator"
            android:label="@string/app_name" >
            </activity>

            <activity
            android:name="com.example.bmiworking.weightgain"
            android:label="@string/app_name" >
            </activity>
            <activity
            android:name="com.example.bmiworking.weightloss"
            android:label="@string/app_name" >
            </activity>
            </application> 
</manifest>

Answer 1

当您在 list 中声明您的 Activity 时，尝试删除 Activity 名称前的包，这样您就可以得到 android:name=".MainActivity" 并对您的其他 Activity 执行相同的操作。

好吧，我的第一个答案是错误的。您的应用程序崩溃的原因是因为您已将主要 Activity 声明为抽象 Activity ，删除此内容后您的应用程序应该可以运行。