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自定义view的简单使用

程序员文章站 2022-05-30 20:26:40
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1.目标:继承textview,重写onDraw(),让view中间有一根线

public class MyTextView extends TextView {
    private Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
    private int lastx;
    private int lasty;

    public MyTextView(Context context) {
        super(context);
        initdraw();
    }

    public MyTextView(Context context, AttributeSet attrs) {
        super(context, attrs);
        initdraw();
    }

    private void initdraw() {
        paint.setColor(Color.RED);
        paint.setStrokeWidth(1.5f);
    }

    public boolean onTouchEvent(MotionEvent event){
        int xx = (int) event.getX(); //在控件中的x
        int yy = (int) event.getY();

        switch(event.getAction()){
            case MotionEvent.ACTION_DOWN:
                lastx = xx;
                lasty = yy;
                break;

            case MotionEvent.ACTION_MOVE:
                setText("" + new Random().nextInt(10));
                int offsetx = xx - lastx; //得到偏移的距离
                int offsety = yy - lasty;

                /*//这是第一种方法layout()
                layout(getLeft()+offsetx ,
                        getTop() + offsety,
                        getRight() + offsetx,
                        getBottom() + offsety); //在移动过程中,不断重绘位置*/

                //第二种方法
                offsetLeftAndRight(offsetx);
                offsetTopAndBottom(offsety);

                //第三种方法(父布局.LayoutParams)如LinearLayout.layoutparams和RelativeLayout.layoutparams
                // 或者是ViewGroup.MarginLayoutParams
                /*ViewGroup.MarginLayoutParams params = (ViewGroup.MarginLayoutParams) getLayoutParams();
                params.leftMargin = getLeft() + offsetx;
                params.topMargin = getTop() + offsety;
                setLayoutParams(params);*/
                /*//(父布局.LayoutParams)
                LinearLayout.LayoutParams layoutParams = (LinearLayout.LayoutParams) getLayoutParams();
                layoutParams.leftMargin = getLeft() + offsetx;
                layoutParams.topMargin = getTop() + offsety;
                setLayoutParams(layoutParams);*/

                //第4中方法scrollby(或者scrollto)这个是移动手机屏幕观看不动的画布,所以要相反移动
                //这种方法是瞬间的。体验并不好,除非用scroller来过度
                //((View)getParent()).scrollBy(-offsetx , -offsety);

                //第5中方法,scroller配合view的comeputeScroll()
                //实现向右移动,代码在上
                break;
        }
        return true;
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        int width = getWidth();
        int height = getHeight();
        canvas.drawLine(width/2 , 0 , width/2 , height , paint);
    }


}
<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content">

<com.example.liuyan.tview1.MyTextView
    android:id="@+id/t1t1"
    android:text="123456"
    android:background="#a9289b38"
    android:layout_width="50dp"
    android:layout_height="50dp"/>
</LinearLayout>

2.目标:继承view

public class RectView extends View {
    private Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
    private int mcolor = Color.RED;

    public RectView(Context context) {
        super(context);
        initdraw();
    }

    public RectView(Context context, AttributeSet attrs) {
        super(context, attrs);

        //如果有自定义的属性要用到,需加入下列代码:
        TypedArray typearray = context.obtainStyledAttributes(attrs , R.styleable.RectView);
        mcolor = typearray.getColor(R.styleable.RectView_rect_color , Color.RED);//没有设置该属性,默认为第2参数
        typearray.recycle();//获取资源必须及时回收

    initdraw();
    }

    private void initdraw() {
        paint.setColor(mcolor);
        paint.setStrokeWidth(1.5f);
    }

    @Override
    public void onDraw(Canvas canvas) {
        super.onDraw(canvas); //默认的不计算padding
        /*//没有对padding做出改变,padding属性无效
        int width = getWidth();
        int height = getHeight();
        canvas.drawRect(0 , 0 , width , height , paint);*/

        //设置对layoutpadding的改变
        int paddingleft = getPaddingLeft();
        int paddingright = getPaddingRight();
        int paddingtop = getPaddingTop();
        int paddingbottom = getPaddingBottom();
        int width = getWidth() - paddingleft - paddingright;
        int height = getHeight() - paddingtop - paddingbottom;
        canvas.drawRect(paddingleft , paddingtop , paddingleft+width , paddingtop+height , paint);
    }

    //如果不对specMode分别处理,则wrap_content和match_parent的效果是一样的
    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        int widthspecmode = MeasureSpec.getMode(widthMeasureSpec);
        int widthspecsize = MeasureSpec.getSize(widthMeasureSpec);
        int heightspecmode = MeasureSpec.getMode(heightMeasureSpec);
        int heightspecsize = MeasureSpec.getSize(heightMeasureSpec);
        if (widthspecmode == MeasureSpec.AT_MOST && heightspecmode == MeasureSpec.AT_MOST){
            //如果宽度和高度都是用了wrap_content
            setMeasuredDimension(400 , 400);//默认的为setMeasureDimension(getDefaultSiza(getSuggestedMinimumWidth() , height一样写法)
        } else if (widthspecmode == MeasureSpec.AT_MOST){
            //只有宽度为wrap_content
            setMeasuredDimension(400 , heightspecsize);
        } else if (heightspecmode == MeasureSpec.AT_MOST){
            setMeasuredDimension(widthspecsize , 400);
        }

    }

}

自定义属性在values/attrs.xml中

自定义view的简单使用

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <declare-styleable name="RectView">
        <attr name="rect_color" format="color"/>

    </declare-styleable>


</resources>

layout

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <com.example.liuyan.tview1.RectView
        xmlns:app="http://schemas.android.com/apk/res-auto"
        android:background="#8961bd57"
        android:layout_width="wrap_content"
        android:layout_height="200dp"
        android:padding="50dp"
        app:rect_color="#a7c7ac13"
        />

</LinearLayout>