javaandroidcanvasandroid-canvassurfaceview
Draw on Android's surfaceView
I want to paint black on surfaceView when i click the button but, it's seems like i'm messing something with my code, it's always white, i've tested the button and it's works:
SurfaceView surfaceView;
SurfaceHolder holder;
Canvas canvas;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main_layout);
surfaceView = (SurfaceView) findViewById(R.id.surfaceView);
surfaceView.getHolder().addCallback(this);
ImageButton paintInBlack;
paintInBlack = (ImageButton) findViewById(R.id.button1);
paintInBlack .setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Log.d( "test", "test" );
Canvas canvas = new Canvas(mBitmap);
Paint blackPaint = new Paint();
blackPaint.setColor(Color.BLACK);
blackPaint.setStyle(Paint.Style.FILL);
canvas.drawPaint(blackPaint);
canvas = holder.lockCanvas();
canvas.drawColor(Color.TRANSPARENT, PorterDuff.Mode.CLEAR);
holder.unlockCanvasAndPost(canvas);
}
Where i'm doing wrong? Thank you !
Solution
Use the following example to achieve what you want:
1) MainActivity.class:
public class MainActivity extends AppCompatActivity {
private final String TAG = MainActivity.class.getSimpleName();
private Button b_draw_all;
private Button b_draw_color;
private Button b_draw_bitmap;
private Button b_draw_text;
private Button b_clear;
private SurfaceView sv;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
b_clear = (Button) findViewById(R.id.b_clear);
b_clear.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
if (sv.getHolder().getSurface().isValid()) {
Canvas canvas = sv.getHolder().lockCanvas();
clearCanvas(canvas);
sv.getHolder().unlockCanvasAndPost(canvas);
}
}
});
b_draw_color = (Button) findViewById(R.id.b_draw_color);
b_draw_color.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
if (sv.getHolder().getSurface().isValid()) {
Canvas canvas = sv.getHolder().lockCanvas();
clearCanvas(canvas);
drawColor(canvas, Color.MAGENTA);
sv.getHolder().unlockCanvasAndPost(canvas);
}
}
});
b_draw_bitmap = (Button) findViewById(R.id.b_draw_bitmap);
b_draw_bitmap.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
if (sv.getHolder().getSurface().isValid()) {
Canvas canvas = sv.getHolder().lockCanvas();
clearCanvas(canvas);
Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.image);
drawBitmap(canvas, bitmap);
sv.getHolder().unlockCanvasAndPost(canvas);
}
}
});
b_draw_text = (Button) findViewById(R.id.b_draw_text);
b_draw_text.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
if (sv.getHolder().getSurface().isValid()) {
Canvas canvas = sv.getHolder().lockCanvas();
clearCanvas(canvas);
drawText(canvas, "Android");
sv.getHolder().unlockCanvasAndPost(canvas);
}
}
});
b_draw_all = (Button) findViewById(R.id.b_draw_all);
b_draw_all.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
if (sv.getHolder().getSurface().isValid()) {
Canvas canvas = sv.getHolder().lockCanvas();
//order is important
//draw color, bitmap and then text
drawColor(canvas, Color.MAGENTA);
Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.image);
drawBitmap(canvas, bitmap);
drawText(canvas, "Android");
sv.getHolder().unlockCanvasAndPost(canvas);
}
}
});
sv = (SurfaceView) findViewById(R.id.sv);
sv.post(new Runnable() {
@Override
public void run() {
if (sv.getHolder().getSurface().isValid()) {
Canvas canvas = sv.getHolder().lockCanvas();
clearCanvas(canvas);
sv.getHolder().unlockCanvasAndPost(canvas);
}
}
});
}
private int[] getSurfaceDimensions(){
return new int[]{sv.getWidth(), sv.getHeight()};
}
/**
*
* @param canvas
* @param color color
*/
private void drawColor(Canvas canvas, int color){
canvas.drawColor(color, PorterDuff.Mode.SRC);
}
private void drawBitmap(Canvas canvas, Bitmap bitmap){
int[] surfaceDimensions = getSurfaceDimensions();
Paint paint = new Paint();
paint.setAntiAlias(true);
paint.setColor(Color.CYAN);
paint.setStyle(Paint.Style.FILL);
paint.setTextSize(100);
paint.setTextAlign(Paint.Align.CENTER);
Rect rectE = new Rect(surfaceDimensions[0] / 4, surfaceDimensions[1] / 4,
3 * surfaceDimensions[0] / 4, 3 * surfaceDimensions[1] / 4);
canvas.drawBitmap(bitmap, null, rectE, paint);
}
private void drawText(Canvas canvas, String text){
int[] surfaceDimensions = getSurfaceDimensions();
Paint paint = new Paint();
paint.setAntiAlias(true);
paint.setColor(Color.CYAN);
paint.setStyle(Paint.Style.FILL);
paint.setTextSize(100);
paint.setTextAlign(Paint.Align.CENTER);
canvas.drawText(text, surfaceDimensions[0]/ 2f,
surfaceDimensions[1] / 2f, paint);
}
private void clearCanvas(Canvas canvas) {
drawColor(canvas, Color.WHITE);
}
}
2) activity_main.xml:
<?xml version="1.0" encoding="utf-8"?>
<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:background="@android:color/white"
tools:context=".MainActivity">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:id="@+id/ll"
android:padding="10dp"
android:layout_weight="100">
<Button
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_weight="50"
android:text="Draw All"
android:textSize="20sp"
android:textColor="@color/colorAccent"
android:background="@android:color/transparent"
android:textAllCaps="false"
android:id="@+id/b_draw_all"/>
<Button
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_weight="50"
android:text="Clear"
android:textSize="20sp"
android:textColor="@color/colorAccent"
android:background="@android:color/transparent"
android:textAllCaps="false"
android:id="@+id/b_clear"/>
</LinearLayout>
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="@id/ll"
android:id="@+id/rl">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:id="@+id/ll1"
android:padding="10dp"
android:layout_weight="100">
<Button
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_weight="50"
android:text="Draw Color"
android:textSize="20sp"
android:textColor="@color/colorAccent"
android:background="@android:color/transparent"
android:textAllCaps="false"
android:id="@+id/b_draw_color"/>
<Button
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_weight="50"
android:text="Draw Bitmap"
android:textSize="20sp"
android:textColor="@color/colorAccent"
android:background="@android:color/transparent"
android:textAllCaps="false"
android:id="@+id/b_draw_bitmap"/>
</LinearLayout>
<Button
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Draw Text"
android:textSize="20sp"
android:layout_below="@id/ll1"
android:textColor="@color/colorAccent"
android:background="@android:color/transparent"
android:textAllCaps="false"
android:id="@+id/b_draw_text"/>
</RelativeLayout>
<SurfaceView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_below="@id/rl"
android:id="@+id/sv"/>
</RelativeLayout>
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