Android進階——自定義View之雙向選擇Seekbar

android 原生的seekbar只能單向選擇滑動，當專案需要選取範圍的時候，這明顯是不能夠滿足要求的。所以就得自己實現一個雙向滑動的Seekbar了，就取名為DoubleSeekBar吧。 而自定義View由是Android知識點中必須掌握的技能所以，這裡就寫一下自己的實現吧。著急的同學，可以直接拷貝程式碼直接使用。 由於佈局比較簡單，這裡直接繼承View，然後重寫onLayout(),onMeasure(),onDraw()方法，程式碼裡註釋比較齊全，想多瞭解的，可以看著註釋理解下。 程式碼如下：

public class DoubleSeekBar extends View {
    private static final String TAG = "DoubleSeekBar";
    private static final int CLICK_TYPE_NULL = 0;
    private static final int CLICK_TYPE_LEFT = 1;
    private static final int CLICK_TYPE_RIGHT = 2;

    private Bitmap leftIcon;
    private Bitmap rightIcon;
    private Bitmap clickIcon;

    private int maxValue;//最大值
    private int minValue;//最小值
    private int leftValue, rightValue;
    private int defaultWidth = 0;
    private int defaultHeight = 0;

    private float bgHeight;
    private float paddingLeft, paddingRight;
    private float indexLeftX, indexLeftY;//左按鈕的座標值
    private float indexRightX, indexRightY;//右按鈕的座標值

    private int viewWidth, viewHeight;
    private float startLeftX, startRightX;//左右按鈕的開始x軸座標值

    private int clickedType = CLICK_TYPE_NULL;//0 沒有點選，1點選中左按鈕，2點選中右按鈕

    private Paint paintBg = new Paint(Paint.ANTI_ALIAS_FLAG);
    private Paint paintBg2 = new Paint(Paint.ANTI_ALIAS_FLAG);
    private Paint iconPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
    private OnChanged mOnChanged;


    public DoubleSeekBar(Context context) {
        this(context, null);
    }

    public DoubleSeekBar(Context context, @Nullable AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public DoubleSeekBar(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        bgHeight = UIUtil.dp2px(context, 2);//設定背景線條的高度

        leftIcon = getBitmap(R.drawable.double_seek_bar_icon);
        rightIcon = getBitmap(R.drawable.double_seek_bar_icon);
        clickIcon = getBitmap(R.drawable.double_seek_bar_click_icon);
        paddingLeft = UIUtil.dp2px(context, 16);
        paddingRight = UIUtil.dp2px(context, 16);

        paintBg.setColor(getResources().getColor(R.color.md_red_A400));
        paintBg2.setColor(getResources().getColor(R.color.md_grey_400));
        maxValue = 100;//default maxvalue
        minValue = 0;//default minvalue
        leftValue = minValue;
        rightValue = maxValue;

        defaultWidth = UIUtil.dp2px(context, 100);
        defaultHeight = UIUtil.dp2px(context, 50);
        setLayerType(LAYER_TYPE_SOFTWARE, null);
    }

    private Bitmap getBitmap(int drawableRes) {
        Drawable drawable = getResources().getDrawable(drawableRes);
        Canvas canvas = new Canvas();
        Bitmap bitmap = Bitmap.createBitmap(drawable.getIntrinsicWidth(), drawable.getIntrinsicHeight(), Bitmap.Config.ARGB_8888);
        canvas.setBitmap(bitmap);
        drawable.setBounds(0, 0, drawable.getIntrinsicWidth(), drawable.getIntrinsicHeight());
        drawable.draw(canvas);

        return bitmap;
    }

    public void setMaxValue(int maxValue) {
        if (maxValue < 0) {
            maxValue = 0;
        }
        this.maxValue = maxValue;
    }

    public void setMinValue(int minValue) {
        if (minValue < 0) {
            minValue = 0;
        }
        this.minValue = minValue;
    }

    public void setOnChanged(OnChanged mOnChanged) {
        this.mOnChanged = mOnChanged;
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                if (isClickedIcon(event)) {
                    postInvalidate();
                    return true;
                }
                break;
            case MotionEvent.ACTION_UP:
                clickedType = CLICK_TYPE_NULL;
                postInvalidate();
                break;
            case MotionEvent.ACTION_MOVE:
                if (handleMoveEvent(event)) {
                    return true;
                }
                break;
            default:
                break;
        }
        return super.onTouchEvent(event);
    }

    /**
     * 判斷是否點選到按鈕了
     *
     * @param event
     * @return
     */
    private boolean isClickedIcon(MotionEvent event) {
        float x = event.getX();
        float y = event.getY();

        if (x < indexLeftX + leftIcon.getWidth() && x > indexLeftX && y > indexLeftY && y < indexLeftY + leftIcon.getHeight()) {
            clickedType = CLICK_TYPE_LEFT;
            return true;
        }

        if (x < indexRightX + rightIcon.getWidth() && x > indexRightX && y > indexRightY && y < indexRightY + rightIcon.getHeight()) {
            clickedType = CLICK_TYPE_RIGHT;
            return true;
        }
        clickedType = CLICK_TYPE_NULL;

        return false;
    }

    /**
     * 滑動事件處理
     *
     * @param motionEvent
     */
    private boolean handleMoveEvent(MotionEvent motionEvent) {
        Log.d(TAG, "handleMoveEvent: start");
        float x = motionEvent.getX();
        if (clickedType == CLICK_TYPE_LEFT) {
            if (x < indexRightX - leftIcon.getWidth() && x > startLeftX) {//左按鈕的範圍小於右按鈕的位置，大於初始值位置
                indexLeftX = x;
            }
            Log.d(TAG, "handleMoveEvent: start indexLeftX = " + indexLeftX);
        } else if (clickedType == CLICK_TYPE_RIGHT) {
            if (x > indexLeftX + rightIcon.getWidth() && x < startRightX) {//右按鈕的範圍大於左按鈕的位置，小於初始值位置
                indexRightX = x;
            }
            Log.d(TAG, "handleMoveEvent: start indexRightX = " + indexRightX);
        }

        leftValue = (int) ((maxValue - minValue) * (indexLeftX - startLeftX) / (startRightX - startLeftX));

        rightValue = (int) ((maxValue - minValue) * (indexRightX - startLeftX) / (startRightX - startLeftX));

        if (mOnChanged != null) {
            mOnChanged.onChange(leftValue, rightValue);
        }
        Log.d(TAG, "handleMoveEvent: start leftValue = " + leftValue + " rightValue = " + rightValue);
        postInvalidate();
        return true;
    }

    @Override
    protected void onFinishInflate() {
        super.onFinishInflate();

    }


    /**
     * 注意，在LinearLayout佈局中，設定weight = 1時，onlayout 會多次回撥，導致indexL(/R)X值一直為預設值，導致無法滑動
     * 可以將佈局改成releativeLayout。
     * @param changed
     * @param left
     * @param top
     * @param right
     * @param bottom
     */
    @Override
    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
        super.onLayout(changed, left, top, right, bottom);
        Log.d(TAG, "onLayout: ");
        viewWidth = getWidth();
        viewHeight = getHeight();

        //左右按鈕的初始值位置計算
        startLeftX = 0 + paddingLeft - leftIcon.getWidth() / 2;
        indexLeftX = startLeftX;
        indexLeftY = viewHeight / 2 - bgHeight / 2 - leftIcon.getHeight() / 2;



        startRightX = viewWidth - paddingRight - rightIcon.getWidth() / 2;
        indexRightX = startRightX;
        indexRightY = viewHeight / 2 - bgHeight / 2 - rightIcon.getHeight() / 2;


        leftValue = (int) ((maxValue - minValue) * (indexLeftX - startLeftX) / (startRightX - startLeftX));

        rightValue = (int) ((maxValue - minValue) * (indexRightX - startLeftX) / (startRightX - startLeftX));
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        Log.d(TAG, "onDraw: getWidth = " + viewWidth);
        drawBg(canvas);
        drawLeftIcon(canvas);
        drawRightIcon(canvas);
    }

    /**
     * 繪製背景
     *
     * @param canvas
     */
    private void drawBg(Canvas canvas) {

        paintBg.setAntiAlias(true);


        //畫兩端的半圓
        float circleLeftCenterX = 0 + paddingLeft;
        float circleRightCenterX = viewWidth - paddingRight;
        canvas.drawCircle(circleLeftCenterX, viewHeight / 2, bgHeight / 2, paintBg);
        canvas.drawCircle(circleRightCenterX, viewHeight / 2, bgHeight / 2, paintBg);

        canvas.drawRect(
                new RectF(circleLeftCenterX, viewHeight / 2 - bgHeight / 2, circleRightCenterX, viewHeight / 2 + bgHeight / 2)
                , paintBg);

        //左右按鈕滑動區域之外繪製其他顏色
        int centerLeftIconX = (int) (indexLeftX + leftIcon.getWidth() / 2);//左按鈕圖示的中心點
        int centerRightIconX = (int) (indexRightX + rightIcon.getWidth() / 2);//右按鈕圖示的中心點

        if (centerLeftIconX > circleLeftCenterX) {
            canvas.drawCircle(circleLeftCenterX, viewHeight / 2, bgHeight / 2, paintBg2);

            canvas.drawRect(
                    new RectF(circleLeftCenterX, viewHeight / 2 - bgHeight / 2, centerLeftIconX, viewHeight / 2 + bgHeight / 2)
                    , paintBg2);
        }

        if (centerRightIconX < circleRightCenterX) {
            canvas.drawCircle(circleRightCenterX, viewHeight / 2, bgHeight / 2, paintBg2);
            canvas.drawRect(
                    new RectF(centerRightIconX, viewHeight / 2 - bgHeight / 2, circleRightCenterX, viewHeight / 2 + bgHeight / 2)
                    , paintBg2);
        }
    }

    /**
     * 繪製左按鈕
     * @param canvas
     */
    private void drawLeftIcon(Canvas canvas) {
        if (clickedType == CLICK_TYPE_LEFT) {
            iconPaint.setMaskFilter(new BlurMaskFilter(50, BlurMaskFilter.Blur.INNER));

            canvas.drawBitmap(clickIcon, indexLeftX, indexLeftY, iconPaint);
        } else {
            iconPaint.setMaskFilter(null);
            canvas.drawBitmap(leftIcon, indexLeftX, indexLeftY, iconPaint);
        }
    }

    /**
     * 繪製右按鈕
     * @param canvas
     */
    private void drawRightIcon(Canvas canvas) {
        Log.d(TAG, "drawLeftIcon: getWidht = " + viewWidth + " indexRightX= " + indexRightX + " indexRightY = " + indexRightY);
        if (clickedType == CLICK_TYPE_RIGHT) {
            iconPaint.setMaskFilter(new BlurMaskFilter(50, BlurMaskFilter.Blur.INNER));
            canvas.drawBitmap(clickIcon, indexRightX, indexRightY, iconPaint);
        } else {
            iconPaint.setMaskFilter(null);
            canvas.drawBitmap(rightIcon, indexRightX, indexRightY, iconPaint);

        }
    }


    /**
     * 回撥介面，回撥左右值
     */
    public interface OnChanged {
        void onChange(int leftValue, int rightValue);
    }


    /**
     * 重寫onMeasure方法，設定wrap_content 時需要預設大小
     *
     * @param widthMeasureSpec
     * @param heightMeasureSpec
     */
    @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) {
            setMeasuredDimension(defaultWidth, defaultHeight);
        } else if (widthSpecMode == MeasureSpec.AT_MOST) {
            setMeasuredDimension(defaultWidth, heightSpecSize);
        } else if (heightSpecMode == MeasureSpec.AT_MOST) {
            setMeasuredDimension(widthSpecSize, defaultHeight);
        }
    }
}
複製程式碼

左右按鈕的Drawable xml佈局（一個正常狀態的，一個按壓狀態的）如下： double_seek_bar_click_icon.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item>
        <shape android:shape="oval">
            <solid android:color="@color/md_red_A700" />
            <size android:width="12dp" android:height="12dp"></size>
        </shape>
    </item>
</selector>
複製程式碼

double_seek_bar_icon.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item>
        <shape android:shape="oval">
            <solid android:color="@color/md_red_A400" />
            <size android:width="12dp" android:height="12dp"></size>
        </shape>
    </item>
</selector>
複製程式碼

使用：

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

        final TextView txtLeft = findViewById(R.id.txt_left);
        final TextView txtRight = findViewById(R.id.txt_right);
        DoubleSeekBar doubleSeekBar = findViewById(R.id.double_seek_bar);
        doubleSeekBar.setMinValue(0);
        doubleSeekBar.setMaxValue(100);
        doubleSeekBar.setOnChanged(new DoubleSeekBar.OnChanged() {
            @Override
            public void onChange(int leftValue, int rightValue) {
                txtLeft.setText(String.valueOf(leftValue));
                txtRight.setText(String.valueOf(rightValue));
            }
        });
    }
複製程式碼

效果如下：