CODEWITHSUNDEEP
javaandroidandroid-studio
Madusha Silva
Madusha Silva

Reputation: 65

Why wont the draw() command draw my circle

I want to create a ball every time someone touches the screen, but i can't seem to get it to work. I want it to be created in a certain location and spawn a ball. There is an if statement which sees if there is a tap on the screen, and in the if statement it calls the draw that is made below to draw a circle in the window.

package com.example.madusha.gravityball;

import android.app.Activity;
import android.content.Intent;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.os.Bundle;
import android.view.KeyEvent;
import android.view.View;
import android.widget.Button;

public class GameWindow extends Activity {
private Paint paint;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_game_window);

    Button pause = (Button) findViewById(R.id.pausebutton);
    pause.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view){
            Intent intent = new Intent(GameWindow.this, PauseMenu.class);
            startActivity(intent);
        }
    });
}

public boolean onKeyDown(int keyCode, KeyEvent event) {
    int Action = event.getAction();
    if(Action == KeyEvent.ACTION_DOWN){
        onDraw();
        System.out.println("Works???");
        return true;
    }
    return super.onKeyDown(keyCode,event);
}
public void init() {
    paint = new Paint();
    paint.setColor(Color.BLUE);
}
Canvas canvas;
public void onDraw(){
    init();
    int height = 100;
    int width = 100;
    canvas.drawCircle(width, height,100,paint);
}
}

Upvotes: 0

Views: 73

Answers (2)

Patrick Cavanagh
Patrick Cavanagh

Reputation: 91

Drawing to a canvas can only be done inside a View object, not an activity like the one that you have in the example. You could create your own custom view something like this - 

public class CustomView extends View {

private Paint paint;

public CompletionSliderView(Context context) {
    super(context);
    init();
}

private void init() {
    paint = new Paint();
    paint.setColor(Color.BLUE);
}

@Override
protected void onDraw(Canvas canvas) {
    int height = getMeasuredHeight();
    int width = getMeasuredWidth();
    canvas.drawCircle(width/2, height/2, height/2, paint);
}

}

To use this in an xml layout, you will need to do this, replacing the package name (probably com.yourcompany.yourapp).

<com.yourcompany.yourapp.CustomView
    android:layout_width="64dp"
    android:layout_height="64dp"/>

You can create a new view in code by doing

View circle = new CustomView(getContext());

Then you can add this to your layout.

Upvotes: 1

Yashodhan
Yashodhan

Reputation: 135

You need to use the OnDraw() function. That is what updates the canvas when drawing stuff.

Upvotes: 1

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