Android 开发（11）图形图像处理技术

绘图

一、画笔（Paint）和画布（Canvas）

• 就是自定义View，继承View，重写ondraw方法
• onDraw里面创建画笔的对象设置相关的参数
• 调用canvas 的方法绘图，需要设置画笔
• 说明：设置画笔的颜色的时候一定要设置透明度，安卓默认是完全透明的，不这设置的话就看不到了

二、绘制几何图形

绘制安卓机器人

public class Robot extends View {
    public Robot(Context context) {
        super(context);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        //define paint
        Paint paint = new Paint();
        paint.setColor(0xFF7FB446);
        paint.setAntiAlias(true);

        //draw head
        RectF rectF_head = new RectF(100, 100, 200, 200);
        canvas.drawArc(rectF_head, -10, -160, false, paint);

        // draw eyes
        paint.setColor(0xFFFFFFFF);
        canvas.drawCircle(125, 125, 3, paint);
        canvas.drawCircle(175, 125, 3, paint);

        //draw ears
        paint.setColor(0xFF7FB446);
        paint.setStrokeWidth(4);
        canvas.drawLine(100, 100, 120, 120, paint);
        canvas.drawLine(200, 100, 172, 120, paint);

        //draw body
        RectF rectF_body = new RectF(100, 150, 200, 250);
        canvas.drawRect(rectF_body, paint);
        rectF_body = new RectF(100, 200, 200, 260);
        canvas.drawRoundRect(rectF_body, 10, 10, paint);

        //draw legs
        RectF rectF_leg = new RectF(125, 250, 145, 300);
        canvas.drawRoundRect(rectF_leg, 10, 10, paint);
        rectF_leg = new RectF(155, 250, 175, 300);
        canvas.drawRoundRect(rectF_leg, 10, 10, paint);

        //draw arms
        RectF rectF_arms = new RectF(70, 150, 90, 230);
        canvas.drawRoundRect(rectF_arms, 10, 10, paint);
        rectF_arms = new RectF(210, 150, 230, 230);
        canvas.drawRoundRect(rectF_arms, 10, 10, paint);
    }
}

三、绘制文本

paint.setTextAlign(Paint.Align.LEFT);
paint.setTextSize(12);
canvas.drawText("文字绘制测试",100,400,paint);

四、绘制图片

1、Bitmap & BitmapFactory

2、示例代码

• 这里是分别用 bitmap 和 bitmapFactory 绘制

Paint paint = new Paint();
String path = (Environment.getExternalStorageDirectory())+"/robot.jpg";
Bitmap bitmap = BitmapFactory.decodeFile(path);
canvas.drawBitmap(bitmap,0,0,paint);
//下面的代码对图片进行了截取
Bitmap bitmap2 = Bitmap.createBitmap(bitmap,0,0,234,300);
canvas.drawBitmap(bitmap2,250,0,paint);

• 以上的代码实现需要通过DDMS上传一张名为 robot.jpg 的图片到模拟器的 sdcard
• 为了保证能够获取到图片，需要在配置访问 sd 卡的权限，如下所示，同时模拟器上开启应用的访问权限

<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE">uses-permission>

五、绘制路径

Paint paint = new Paint();
paint.setAntiAlias(true);
paint.setColor(0xFF000000);
paint.setStyle(Paint.Style.STROKE);
Path path = new Path();
path.addCircle(200,200,100,Path.Direction.CCW);
//canvas.drawPath(path,paint);
String str = "test module test moduletest module test module test moduletest module test module";
canvas.drawTextOnPath(str,path,0,0,paint);

---

动画

一、逐帧动画

• 准备动画资源

<animation-list xmlns:android="http://schemas.android.com/apk/res/android">
    <item
        android:drawable="@drawable/img001"
        android:duration="60" />
    <item
        android:drawable="@drawable/img002"
        android:duration="60" />
    <item
        android:drawable="@drawable/img003"
        android:duration="60" />
    <item
        android:drawable="@drawable/img004"
        android:duration="60" />
    <item
        android:drawable="@drawable/img005"
        android:duration="60" />
    <item
        android:drawable="@drawable/img006"
        android:duration="60" />
animation-list>

• 使用动画资源：这里的 fairy xml 动画资源是放置在drawable目录下的

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/lay"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@drawable/fairy"
    android:orientation="vertical"
    tools:context=".MainActivity">
LinearLayout>

• 控制动画播放：默认使用横屏可以在 manifest 相应的 activity 设置属性android:screenOrientation="landscape"

public class MainActivity extends AppCompatActivity {
    private boolean flag = true;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        LinearLayout linearLayout = (LinearLayout) findViewById(R.id.lay);
        final AnimationDrawable animation = (AnimationDrawable) linearLayout.getBackground();

        linearLayout.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (flag) {
                    animation.start();
                    flag = false;
                } else {
                    animation.stop();
                    flag = true;
                }
            }
        });
    }
}

二、补间动画

1、补间动画的概念

• 补间动画就是我们只需要提供初始的帧和最终的帧，安卓会帮我们自动补上动画中间的帧
• 但是补间动画不是万能，安卓只支持如下的四种，分别用如下的标记来定义
  

2、旋转动画的实现

• 动画资源：这些动画资源是放在anim文件夹下的

<set xmlns:android="http://schemas.android.com/apk/res/android">
    <rotate
        android:fromDegrees="0"
        android:pivotX="50%"
        android:pivotY="50%"
        android:toDegrees="360"
        android:duration="2000"/>
set>

• MainActivity

final ImageView imageView = (ImageView)findViewById(R.id.iv);
imageView.setOnClickListener(new View.OnClickListener() {
	@Override
	public void onClick(View v) {
		Animation animation = AnimationUtils.loadAnimation(MainActivity.this,R.anim.anim_rotate);
		imageView.startAnimation(animation);
	}
});