I am developing app for kids drawing alphabet according to alphabet stroke. I cannot run DrawingActivity cause by java.lang.NullPointerException.I not really strong in coding. I feel that null error come from getIntent().getExtras().getString("type");.So,i change the code to getIntent().getStringExtra("type");,but still can't run DrawingActivity. Please help me guys. Really appreciate it.
This is my error logcat:
12-05 23:47:29.498 9620-9620/com.example.user.mygame E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.user.mygame, PID: 9620
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.user.mygame/com.example.user.mygame.DrawingActivity}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2198)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2247)
at android.app.ActivityThread.access$800(ActivityThread.java:141)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1210)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5111)
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:806)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:622)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at com.example.user.mygame.DrawingActivity.onCreate(DrawingActivity.java:156)
at android.app.Activity.performCreate(Activity.java:5248)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2162)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2247)
at android.app.ActivityThread.access$800(ActivityThread.java:141)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1210)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5111)
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:806)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:622)
at dalvik.system.NativeStart.main(Native Method)
This is my DrawingActivity.java:
package com.example.user.mygame;
import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Paint.Cap;
import android.graphics.Paint.Join;
import android.graphics.Paint.Style;
import android.graphics.Path;
import android.graphics.Path.Direction;
import android.graphics.Rect;
import android.os.Bundle;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.View.OnTouchListener;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.RelativeLayout.LayoutParams;
import com.google.android.gms.location.DetectedActivity;
import com.google.android.gms.maps.model.BitmapDescriptorFactory;
public class DrawingActivity extends Activity implements OnClickListener, OnTouchListener {
View drawingView;
DrawingView dv;
LayoutParams params;
ViewGroup parent;
ImageView nextBtn;
ImageView playBtn;
ImageView prevBtn;
private Paint mPaint;
private Integer position;
private int totalItem;
private String type;
public class DrawingView extends View {
private static final float TOUCH_TOLERANCE = 4.0f;
private Bitmap bm;
private Paint circlePaint;
private Path circlePath;
Context context;
private Bitmap mBitmap;
private Paint mBitmapPaint;
private Canvas mCanvas;
private Path mPath;
private float mX;
private float mY;
public DrawingView(Context c) {
super(c);
this.context = c;
this.mPath = new Path();
this.mBitmapPaint = new Paint(4);
this.circlePaint = new Paint();
this.circlePath = new Path();
this.circlePaint.setAntiAlias(true);
this.circlePaint.setColor(Color.BLACK);
this.circlePaint.setStyle(Style.STROKE);
this.circlePaint.setStrokeJoin(Join.MITER);
this.circlePaint.setStrokeWidth(TOUCH_TOLERANCE);
}
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
this.mBitmap = Bitmap.createBitmap(w, h, Config.ARGB_8888);
this.mCanvas = new Canvas(this.mBitmap);
if (DrawingActivity.this.type.equals(Resource.DRAWING_ALPHABET)) {
this.bm = BitmapFactory.decodeResource(getResources(), Resource.capitalStoke[DrawingActivity.this.position]);
}
this.mCanvas.drawBitmap(this.bm, new Rect(0, 0, this.bm.getWidth(), this.bm.getHeight()), new Rect(0, 0, this.mCanvas.getWidth(), this.mCanvas.getHeight()), this.mBitmapPaint);
}
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
canvas.drawBitmap(this.mBitmap, 0.0f, 0.0f, this.mBitmapPaint);
canvas.drawPath(this.mPath, DrawingActivity.this.mPaint);
canvas.drawPath(this.circlePath, this.circlePaint);
}
private void touch_start(float x, float y) {
this.mPath.reset();
this.mPath.moveTo(x, y);
this.mX = x;
this.mY = y;
}
private void touch_move(float x, float y) {
float dx = Math.abs(x - this.mX);
float dy = Math.abs(y - this.mY);
if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) {
this.mPath.quadTo(this.mX, this.mY, (this.mX + x) / 2.0f, (this.mY + y) / 2.0f);
this.mX = x;
this.mY = y;
this.circlePath.reset();
this.circlePath.addCircle(this.mX, this.mY, BitmapDescriptorFactory.HUE_ORANGE, Direction.CW);
}
}
private void touch_up() {
this.mPath.lineTo(this.mX, this.mY);
this.circlePath.reset();
this.mCanvas.drawPath(this.mPath, DrawingActivity.this.mPaint);
this.mPath.reset();
}
public boolean onTouchEvent(MotionEvent event) {
float x = event.getX();
float y = event.getY();
switch (event.getAction()) {
case DetectedActivity.IN_VEHICLE /*0*/:
touch_start(x, y);
invalidate();
break;
case DetectedActivity.ON_BICYCLE /*1*/:
touch_up();
invalidate();
break;
case DetectedActivity.ON_FOOT /*2*/:
touch_move(x, y);
invalidate();
break;
}
return true;
}
public void resetCanvas() {
this.bm = null;
this.mBitmap = null;
System.gc();
}
}
public DrawingActivity() {
this.type = "";
this.position = 0;
this.totalItem = 0;
this.nextBtn = null;
this.playBtn = null;
this.prevBtn = null;
this.drawingView = null;
this.parent = null;
this.params = null;
}
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(1);
setContentView(R.layout.drawing_alphabet);
this.type = getIntent().getExtras().getString("type");
this.nextBtn = (ImageView) findViewById(R.id.nextId);
this.playBtn = (ImageView) findViewById(R.id.playId);
this.prevBtn = (ImageView) findViewById(R.id.prevId);
this.nextBtn.setOnClickListener(this);
this.nextBtn.setOnTouchListener(this);
this.prevBtn.setOnClickListener(this);
this.prevBtn.setOnTouchListener(this);
this.playBtn.setOnClickListener(this);
this.playBtn.setOnTouchListener(this);
this.drawingView = findViewById(R.id.drawingViewId);
this.params = (LayoutParams) this.drawingView.getLayoutParams();
this.dv = new DrawingView(this);
this.dv.setLayoutParams(this.params);
this.parent = (ViewGroup) this.drawingView.getParent();
int index = this.parent.indexOfChild(this.drawingView);
this.parent.removeView(this.drawingView);
this.parent.addView(this.dv, index);
if (this.type.equals(Resource.DRAWING_ALPHABET)) {
this.totalItem = Resource.capitalStoke.length;
}
this.mPaint = new Paint();
this.mPaint.setAntiAlias(true);
this.mPaint.setDither(true);
this.mPaint.setColor(Color.BLACK);
this.mPaint.setStyle(Style.STROKE);
this.mPaint.setStrokeJoin(Join.ROUND);
this.mPaint.setStrokeCap(Cap.ROUND);
this.mPaint.setStrokeWidth(16.0f);
updatePreviousButton();
}
public boolean onTouch(View v, MotionEvent event) {
switch (event.getAction()) {
case DetectedActivity.IN_VEHICLE /*0*/:
if (v.getId() == R.id.nextId || v.getId() == R.id.playId || v.getId() == R.id.prevId) {
v.setAlpha(0.5f);
break;
}
case DetectedActivity.ON_BICYCLE /*1*/:
if (v.getId() == R.id.nextId || v.getId() == R.id.playId || v.getId() == R.id.prevId) {
v.setAlpha(1.0f);
break;
}
}
return false;
}
public void onClick(View v) {
switch (v.getId()) {
case R.id.nextId:
this.position = this.position + 1;
changeStroke();
case R.id.playId:
changeStroke();
case R.id.prevId:
this.position = this.position - 1;
changeStroke();
default:
}
}
private void changeStroke() {
updateNextButton();
updatePreviousButton();
int index = this.parent.indexOfChild(this.dv);
this.dv.resetCanvas();
this.dv = null;
this.parent.removeViewAt(index);
this.dv = new DrawingView(this);
this.dv.setLayoutParams(this.params);
this.parent.addView(this.dv, index);
}
private void updateNextButton() {
if (this.position == this.totalItem - 1) {
this.nextBtn.setAlpha(0.5f);
this.nextBtn.setClickable(false);
return;
}
this.nextBtn.setAlpha(1.0f);
this.nextBtn.setClickable(true);
}
private void updatePreviousButton() {
if (this.position == 0) {
this.prevBtn.setAlpha(0.5f);
this.prevBtn.setClickable(false);
return;
}
this.prevBtn.setAlpha(1.0f);
this.prevBtn.setClickable(true);
}
}
This is my drawing_alphabet.xml:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@drawable/bg_drawing">
<View
android:id="@+id/drawingViewId"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="0dp"
android:layout_marginRight="64dp"
android:layout_marginEnd="64dp"/>
<ImageView
android:id="@+id/prevId"
android:layout_width="52dp"
android:layout_height="52dp"
android:src="@drawable/back_icon"
android:layout_gravity="top"
android:layout_marginTop="49dp"
android:layout_alignParentTop="true"
android:layout_alignLeft="@+id/nextId"
android:layout_alignStart="@+id/nextId" />
<ImageView
android:id="@+id/nextId"
android:layout_width="52dp"
android:layout_height="52dp"
android:src="@drawable/next_icon"
android:layout_gravity="bottom"
android:layout_marginTop="61dp"
android:layout_below="@+id/prevId"
android:layout_alignParentRight="true"
android:layout_alignParentEnd="true" /> /
</RelativeLayout>
This is my manifest.xml:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.user.mygame">
<application
android:allowBackup="false"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:supportsRtl="true"
android:theme="@style/AppTheme"
android:name="android.support.multidex.MultiDexApplication">
<activity android:name=".MainActivity"
android:screenOrientation="landscape">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:label="@string/app_name" android:name="com.example.user.mygame.AlphabetActivity" android:screenOrientation="landscape" />
<activity android:label="@string/app_name" android:name="com.example.user.mygame.DrawingActivity" android:screenOrientation="landscape" />
</application>
</manifest>
This is my resource.java:
package com.example.user.mygame;
public class Resource {
public static String DRAWING_ALPHABET;
public static Integer[] capitalStoke;
Integer[] alphabetCapital;
Integer[] alphabetSound;
Integer[] alphabetImage;
static {
DRAWING_ALPHABET = "alphabet";
setCapitalStoke(new Integer[]{Integer.valueOf(R.drawable.capital_letters_stroke_01),
Integer.valueOf(R.drawable.capital_letters_stroke_02),
Integer.valueOf(R.drawable.capital_letters_stroke_03),
Integer.valueOf(R.drawable.capital_letters_stroke_04),
Integer.valueOf(R.drawable.capital_letters_stroke_05),
Integer.valueOf(R.drawable.capital_letters_stroke_06),
Integer.valueOf(R.drawable.capital_letters_stroke_07),
Integer.valueOf(R.drawable.capital_letters_stroke_08),
Integer.valueOf(R.drawable.capital_letters_stroke_09),
Integer.valueOf(R.drawable.capital_letters_stroke_10),
Integer.valueOf(R.drawable.capital_letters_stroke_11),
Integer.valueOf(R.drawable.capital_letters_stroke_12),
Integer.valueOf(R.drawable.capital_letters_stroke_13),
Integer.valueOf(R.drawable.capital_letters_stroke_14),
Integer.valueOf(R.drawable.capital_letters_stroke_15),
Integer.valueOf(R.drawable.capital_letters_stroke_16),
Integer.valueOf(R.drawable.capital_letters_stroke_17),
Integer.valueOf(R.drawable.capital_letters_stroke_18),
Integer.valueOf(R.drawable.capital_letters_stroke_19),
Integer.valueOf(R.drawable.capital_letters_stroke_20),
Integer.valueOf(R.drawable.capital_letters_stroke_21),
Integer.valueOf(R.drawable.capital_letters_stroke_22),
Integer.valueOf(R.drawable.capital_letters_stroke_23),
Integer.valueOf(R.drawable.capital_letters_stroke_24),
Integer.valueOf(R.drawable.capital_letters_stroke_25),
Integer.valueOf(R.drawable.capital_letters_stroke_26)});
}
public static Integer[] getCapitalStoke() {
return capitalStoke;
}
public static void setCapitalStoke(Integer[] capitalStoke) {
Resource.capitalStoke = capitalStoke;
}
public Resource() {
this.alphabetCapital = new Integer[]{
Integer.valueOf(R.drawable.img_letter_001),
Integer.valueOf(R.drawable.img_letter_002),
Integer.valueOf(R.drawable.img_letter_003),
Integer.valueOf(R.drawable.img_letter_004),
Integer.valueOf(R.drawable.img_letter_005),
Integer.valueOf(R.drawable.img_letter_006),
Integer.valueOf(R.drawable.img_letter_007),
Integer.valueOf(R.drawable.img_letter_008),
Integer.valueOf(R.drawable.img_letter_009),
Integer.valueOf(R.drawable.img_letter_010),
Integer.valueOf(R.drawable.img_letter_011),
Integer.valueOf(R.drawable.img_letter_012),
Integer.valueOf(R.drawable.img_letter_013),
Integer.valueOf(R.drawable.img_letter_014),
Integer.valueOf(R.drawable.img_letter_015),
Integer.valueOf(R.drawable.img_letter_016),
Integer.valueOf(R.drawable.img_letter_017),
Integer.valueOf(R.drawable.img_letter_018),
Integer.valueOf(R.drawable.img_letter_019),
Integer.valueOf(R.drawable.img_letter_020),
Integer.valueOf(R.drawable.img_letter_021),
Integer.valueOf(R.drawable.img_letter_022),
Integer.valueOf(R.drawable.img_letter_023),
Integer.valueOf(R.drawable.img_letter_024),
Integer.valueOf(R.drawable.img_letter_025),
Integer.valueOf(R.drawable.img_letter_026)};
this.alphabetSound = new Integer[]{
Integer.valueOf(R.raw.snd_a),
Integer.valueOf(R.raw.snd_b),
Integer.valueOf(R.raw.snd_c),};
this.alphabetImage = new Integer[]{
Integer.valueOf(R.drawable.image_1),
Integer.valueOf(R.drawable.image_2),
Integer.valueOf(R.drawable.image_3)};
}
}
