“Unfortunately app has stopped” error?

Question

I'm trying to write a basic drawing Android app for android and test it on Genymotion, but I can't click on the app icon (it says "Unfortunately [app] has stopped.")

I'm not sure if the three private variables should be under the MainActivity class? Or that it has to do with my AndroidManifest.xml file. Can someone look over my code?

My MainActivity.java file:

package edu.berkeley.cs160.opalkale.prog2;

import android.os.Bundle;
import android.app.Activity;
import android.graphics.Paint;
import android.view.Menu;
import android.view.View;
import android.widget.ImageButton;
import android.widget.LinearLayout;

public class MainActivity extends Activity {
private Paint myPaint;
private ImageButton currPaint;
private myView drawView;

public void paintClicked(View view) {
    if (view != currPaint) {
        // update color
        ImageButton imgView = (ImageButton) view;
        String color = view.getTag().toString();

        drawView.setColor(color);
        imgView.setImageDrawable(getResources().getDrawable(R.drawable.paint_pressed));
        currPaint.setImageDrawable(getResources().getDrawable(R.drawable.paint));
        currPaint = (ImageButton)view;
    }

}

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    myView mV = new myView(this, null);
    setContentView(mV);

    drawView = (myView) findViewById(R.id.drawing);

    LinearLayout paintLayout = (LinearLayout) findViewById(R.id.paint_colors);
    currPaint = (ImageButton) paintLayout.getChildAt(0);
    currPaint.setImageDrawable(getResources().getDrawable(
            R.drawable.paint_pressed));
}

@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;
}

}

---

My AndroidManifest.xml file:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="edu.berkeley.cs160.opalkale.prog2"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="13"
        android:targetSdkVersion="18" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="edu.berkeley.cs160.opalkale.prog2.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>
    </application>

</manifest>

---

Logcat:

[2014-02-11 23:04:43 - DeviceMonitor] Adb connection Error:EOF
[2014-02-11 23:04:43 - DeviceMonitor] Sending jdwp tracking request failed!
[2014-02-11 23:04:43 - DeviceMonitor] Connection attempts: 1
[2014-02-11 23:04:44 - DeviceMonitor] Connection attempts: 2
[2014-02-11 23:04:45 - DeviceMonitor] Connection attempts: 3
[2014-02-11 23:04:46 - DeviceMonitor] Connection attempts: 4
[2014-02-11 23:04:47 - DeviceMonitor] Connection attempts: 5
[2014-02-11 23:04:48 - DeviceMonitor] Connection attempts: 6
[2014-02-11 23:04:49 - DeviceMonitor] Connection attempts: 7
[2014-02-11 23:04:50 - DeviceMonitor] Connection attempts: 8
[2014-02-11 23:04:51 - DeviceMonitor] Connection attempts: 9
[2014-02-11 23:04:52 - DeviceMonitor] Connection attempts: 10
[2014-02-11 23:04:53 - DeviceMonitor] Connection attempts: 11
[2014-02-11 23:07:14 - Logcat] device not found
com.android.ddmlib.AdbCommandRejectedException: device not found
at com.android.ddmlib.AdbHelper.setDevice(AdbHelper.java:774)
at com.android.ddmlib.AdbHelper.executeRemoteCommand(AdbHelper.java:396)
at com.android.ddmlib.AdbHelper.executeRemoteCommand(AdbHelper.java:347)
at com.android.ddmlib.Device.executeShellCommand(Device.java:444)
at com.android.ddmuilib.logcat.LogPanel$3.run(LogPanel.java:531)

---

activity_main.xml:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:screenOrientation="portrait"
tools:context=".MainActivity" >

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#FFCCCCCC"
    android:orientation="vertical"
    tools:context=".MainActivity" >

    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="50dp"
        android:layout_gravity="center"
        android:orientation="horizontal" >

        <ImageButton
            android:id="@+id/new_btn"
            android:layout_width="wrap_content"
            android:layout_height="fill_parent"
            android:contentDescription="@string/brush"
            android:src="@drawable/brush" />
    </LinearLayout>

    <edu.berkeley.cs160.opalkale.prog2.myView
        android:id="@+id/drawing"
        android:layout_width="fill_parent"
        android:layout_height="0dp"
        android:layout_marginBottom="3dp"
        android:layout_marginLeft="5dp"
        android:layout_marginRight="5dp"
        android:layout_marginTop="3dp"
        android:layout_weight="1"
        android:background="#FFFFFFFF" />

    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:orientation="vertical" >

        <LinearLayout
            android:id="@+id/paint_colors"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:orientation="horizontal" >

            <ImageButton
                android:layout_width="@dimen/large_brush"
                android:layout_height="@dimen/large_brush"
                android:layout_margin="2dp"
                android:background="#FF787878"
                android:contentDescription="@string/paint"
                android:onClick="paintClicked"
                android:src="@drawable/paint"
                android:tag="#FF787878" />
        </LinearLayout>

        </LinearLayout>
    </LinearLayout>

</RelativeLayout>

---

myView class:

package edu.berkeley.cs160.opalkale.prog2;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;

public class myView extends View {
private Path drawPath;
private Paint drawPaint, canvasPaint;
private int paintColor = 0xFF787878;
private Canvas drawCanvas;
private Bitmap canvasBitmap;

public void setColor(String newColor){
    //set color     
    invalidate();
    paintColor = Color.parseColor(newColor);
    drawPaint.setColor(paintColor); 
    }

public myView(Context context, AttributeSet attrs) {
    super(context, attrs);

    setupDrawing();
}

private void setupDrawing() {
    drawPath = new Path();
    drawPaint = new Paint();
    drawPaint.setColor(paintColor);
    drawPaint.setAntiAlias(true);
    drawPaint.setStrokeWidth(20);
    drawPaint.setStyle(Paint.Style.STROKE);
    drawPaint.setStrokeJoin(Paint.Join.ROUND);
    drawPaint.setStrokeCap(Paint.Cap.ROUND);

    canvasPaint = new Paint(Paint.DITHER_FLAG);
}

@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
    // view given size
    super.onSizeChanged(w, h, oldw, oldh);
    canvasBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
    drawCanvas = new Canvas(canvasBitmap);
}

@Override
protected void onDraw(Canvas canvas) {
    // draw view
    canvas.drawBitmap(canvasBitmap, 0, 0, canvasPaint);
    canvas.drawPath(drawPath, drawPaint);
}

@Override
public boolean onTouchEvent(MotionEvent event) {
    // detect user touch
    float touchX = event.getX();
    float touchY = event.getY();

    switch (event.getAction()) {
    case MotionEvent.ACTION_DOWN:
        drawPath.moveTo(touchX, touchY);
        break;
    case MotionEvent.ACTION_MOVE:
        drawPath.lineTo(touchX, touchY);
        break;
    case MotionEvent.ACTION_UP:
        drawCanvas.drawPath(drawPath, drawPaint);
        drawPath.reset();
        break;
    default:
        return false;
    }
    invalidate();
    return true;
}

}

Answer 1

setContentView(Id); is missing in your code.So it is giving you NullPointerException

Set some of the view to your Activity like

setContentView(R.layout.layout);

Answer 2

NPE- Null Pointer Exception. No call to setContentView.

Also,

drawView = (myView) findViewById(R.id.drawing);  

what is your myView ?

Please set myView as the view for your activity or call setContentView with the layout where R.id.drawing is.

Answer 3

It is just a common problem with manifest your program "Unfortunately app has stopped" may be caused due to Manifest file , Because you have two classes:

So use this:

<uses-sdk
    android:minSdkVersion="13"
    android:targetSdkVersion="18" />

<application
    android:allowBackup="true"
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    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=".myView"
      android:label="@string/app_name">
    </activity>
</application>

Answer 4

Where is your layout .Your layout is missing. Use setContentView(R.layout.yourlayout);

Answer 5

只需删除此行中的评论，

// setContentView(mV);