Android学习(23)OntTouch_触摸事件

Android学习(23)OntTouch_触摸事件

OnTouch：触摸事件
通过getPointerCount获取手指数量

1.单点触摸：将图片移动到触摸位置

(1)在布局文件中添加一张图片，给布局文件添加id

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/ivLayout">
    <ImageView
        android:id="@+id/ivST"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/kcbb"/>
</RelativeLayout>

(2)在Activity中设置触摸监听

public class SingleTouchActivity extends AppCompatActivity {

    //定义一个ImageView
    private ImageView iv;
    //声明一个RelativeLayout
    private RelativeLayout layout;
    //声明一个RelativeLayout.LayoutParams用于设置图片位置
    private RelativeLayout.LayoutParams rl;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_single_touch);
        //绑定组建
        iv = (ImageView)findViewById(R.id.ivST);
        layout = (RelativeLayout)findViewById(R.id.ivLayout);
        //对layout设置触摸监听
        layout.setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                //当移动时
                if (event.getAction() == MotionEvent.ACTION_MOVE) {
                    //获取图片位置
                    rl = (RelativeLayout.LayoutParams)iv.getLayoutParams();
                    //获取点击的位置的Y坐标，设置为上边距
                    rl.topMargin = (int)event.getY();
                    //获取点击的位置的X坐标，设置为左
                    rl.leftMargin = (int)event.getX();
                    //设置图片位置
                    iv.setLayoutParams(rl);
                }
                return true;
            }
        });
    }
}

2.多点触控：实现双指缩放图片

(1)新建一个视图，绘制图片

MyMutilTouch.java

public class MyMutilTouch extends SurfaceView implements SurfaceHolder.Callback{

    //实例化Bitmap,用于加载图片
    private Bitmap bitmap;
    //加载图片的矩形框
    private Rect src = new Rect();
    //图片
    private RectF dst = new RectF();
    //实例化一个坐标点对象，用于设置放大倍数
    private PointF scale = new PointF(1,1);

    //构造函数
    public MyMutilTouch(Context context) {
        super(context);
        //回调
        getHolder().addCallback(this);
        //引入图片
        bitmap = ((BitmapDrawable)(getResources().getDrawable(R.drawable.nazi))).getBitmap();
        //确定图片的宽和高
        src.right = bitmap.getWidth();
        src.bottom = bitmap.getHeight();
        dst.right = src.right;
        dst.bottom = src.bottom;
    }
    //绘制图片
    public void draw(){
        //锁定画布
        Canvas canvas = getHolder().lockCanvas();
        //设置背景颜色
        canvas.drawColor(0xffffffff);
        //让绘图保持可编辑、可存储状态
        canvas.save();
        //缩放画布(X轴缩放倍数，Y轴缩放倍数，缩放原点X坐标，缩放原点Y坐标)
        canvas.scale(getScale().x,getScale().y,getWidth()/2,getHeight()/2);
        //绘制图片
        canvas.drawBitmap(bitmap,src,dst,null);
        //画布回滚，释放资源
        canvas.restore();
        //解锁画布
        getHolder().unlockCanvasAndPost(canvas);
    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {

    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
        draw();
    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {

    }

    //控制图片变化，设置图片变化的倍数
    public void scale(float scalex,float scaley){
        getScale().x = scalex;
        getScale().y = scaley;
        draw();
    }

    public PointF getScale() {
        return scale;
    }

    public void setScale(PointF scale) {
        this.scale = scale;
    }
}

(2)在Activity中设置触摸事件监听

public class MutilTouchActivity extends AppCompatActivity implements View.OnTouchListener {

    //声明新的视图
    private MyMutilTouch view;
    private float tance = 0;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //实例化视图
        view = new MyMutilTouch(this);
        //引入视图
        setContentView(view);
        //绑定触摸监听
        view.setOnTouchListener(this);
    }

    @Override
    public boolean onTouch(View v, MotionEvent event) {
        //如果触摸的手指大于2
        if (event.getPointerCount() >= 2) {
            //获取第一个触摸点的X,Y坐标
            float p1_x = event.getX(0);
            float p1_y = event.getY(0);
            //获取第二个触摸点的X,Y坐标
            float p2_x = event.getX(1);
            float p2_y = event.getY(1);
            //获取两个点的X,Y坐标的距离
            float diff_x = p1_x - p2_x;
            float diff_y = p1_y - p2_y;
            //通过勾股定理计算得到两点间的距离
            float distance = (float) Math.sqrt(diff_x * diff_x + diff_y *diff_y);
            //输出两点间的距离
            System.out.println("distance"+distance);
            System.out.println("tancs:"+tance);
            if (tance == 0) {
                tance = distance;
            }else {
                if (distance - tance > 10) {
                    //放大
                    view.scale(view.getScale().x + 0.1f,view.getScale().y + 0.1f);
                    tance = distance;
                }else if(distance - tance < -10){
                    //缩小
                    view.scale(view.getScale().x - 0.1f,view.getScale().y - 0.1f);
                    System.out.println(distance);
                    tance = distance;
                }
            }
            if (event.getAction() == MotionEvent.ACTION_UP) {
                tance = 0;
            }
        }
        return true;
    }
}

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声明：
1.知识点来源于《网易云课堂》——《Android基础视频教程》
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