白板制作

Question

嘿！！我想做一个白板应用程序，但我不知道如何只让一些像素变黑，让其他像素变白。

Answer 1

这将有助于在您的白板上获得黑色像素：

Scribbler.java：

package org.yourpackage.scribble;

import android.app.Activity;
import android.graphics.Color;
import android.os.Bundle;

public class Scribbler extends Activity {
    DrawView drawView;
    
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        drawView = new DrawView(this);
        drawView.setBackgroundColor(Color.WHITE);
        setContentView(drawView);
        drawView.requestFocus();
        
    }
}

DrawView.java：

package org.yourpackage.scribble;

import java.util.ArrayList;
import java.util.List;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;

public class DrawView extends View implements OnTouchListener {
    List<Point> points = new ArrayList<Point>();
    Paint paint = new Paint();

    public DrawView(Context context) {
        super(context);
        setFocusable(true);
        setFocusableInTouchMode(true);
        this.setOnTouchListener(this);
        paint.setColor(Color.BLACK);
    }

    @Override
    public void onDraw(Canvas canvas) {
        for (Point point : points) {
            canvas.drawCircle(point.x, point.y, 2, paint);  
        }
    }

    public boolean onTouch(View view, MotionEvent event) {
        Point point = new Point();
        point.x = event.getX();
        point.y = event.getY();
        points.add(point);
        invalidate();
        return true;
    }
}

class Point {
    float x, y;
}

AndroidManifest.xml：

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="org.yourpackage.scribble"
      android:versionCode="1"
      android:versionName="1.0">
    <application>
        <activity android:name=".Scribbler">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>
    <uses-sdk android:minSdkVersion="3" />
</manifest> 

...which看起来像这样：

​

​

您可能想要绘制线条而不是像素-这一条只是给您一个提示

Answer 2

看看这个。http://www.tutorialforandroid.com/2009/06/drawing-with-canvas-in-android.html

此外，您可能还需要一个web应用程序/服务，以便将屏幕内容传输给您的受众。