Android自定義View實現(xiàn)柱狀波形圖的繪制

更新時間：2022年08月16日 08:50:29 作者：AnRFDev

柱狀波形圖是一種常見的圖形。一個個柱子按順序排列，構(gòu)成一個波形圖。本文將利用Android自定義View實現(xiàn)柱狀波形圖的繪制，需要的可以參考一下

前言

柱狀波形圖是一種常見的圖形。一個個柱子按順序排列，構(gòu)成一個波形圖。

柱子的高度由輸入數(shù)據(jù)決定。如果輸入的是音頻的音量，則可得到一個聲波圖。

在一些音頻軟件中，我們也可以左右拖動聲波，來改變音頻的播放進度

本文舉例的自定View，實現(xiàn)如下功能：

以柱狀形式展示數(shù)據(jù)的大小
標明圖形當前最中間的數(shù)據(jù)
可以橫向拖動進度，進度就是讓某個特定的數(shù)據(jù)居中展示
可以改變左右兩邊的柱子顏色
可以調(diào)整柱子的寬度
拖動完畢后監(jiān)聽當前進度

實現(xiàn)

首先創(chuàng)建類SoundWaveView繼承自View

我們可以先記錄給定的寬高，方便后面找到View的中間點

private int viewWid = 1000;     // px
private int viewHeight = 100;   // px

@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
    super.onSizeChanged(w, h, oldw, oldh);
    viewWid = w;
    viewHeight = h;
    // ..
}

基本屬性

例如柱子的顏色，寬度?？梢栽O(shè)置個屬性來記錄，并開放出去可由外部來設(shè)置。

private float barWidDp = 1.5f;
private float barWidPx = 3f;
private float barGapPx = barWidPx / 2;
private int barCount = 1;       // 當前寬度能繪制多少個柱子

private final Paint paint = new Paint();
private int leftColor = Color.GREEN;
private int rightColor = Color.LTGRAY;
private int middleLineColor = Color.parseColor("#55000000");

設(shè)計監(jiān)聽器

拖動完畢后，可以將當前進度通知出去。也可以直接把觸摸事件傳出去。

public interface OnEvent {
    void onMoveEnd(); // 停止拖動了

    void onDragTouchEvent(MotionEvent event);
}

private OnEvent onEventListener;

private void tellOnMoveEnd() {
    if (onEventListener != null) {
        onEventListener.onMoveEnd();
    }
}

繪制圖形

在onDraw方法中根據(jù)數(shù)據(jù)繪制圖形

本例沒有設(shè)計背景，直接繪制數(shù)據(jù)。

圖形需求之一是要求某個數(shù)據(jù)能居中顯示，我們用midIndex來標記這個數(shù)據(jù)的下標。

比較簡單粗暴的實現(xiàn)方法，遍歷整個數(shù)據(jù)列表，計算出每個數(shù)據(jù)的x坐標。超出范圍的不繪制，范圍內(nèi)的逐一繪制。

@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    if (dataList == null || dataList.isEmpty()) {
        // draw nothing
        drawMiddleLine(canvas);
        return;
    }
    float x0 = viewWid / 2.0f;

    if (midIndex > 0) {
        x0 = x0 - (barGapPx + barWidPx) * midIndex; // 可能是負數(shù)
    }
    for (int i = 0; i < dataList.size(); i++) {
        float d = dataList.get(i);
        float x = x0 + (barWidPx + barGapPx) * i;
        if (x < 0) {
            continue;
        }
        if (x > viewWid) {
            break;
        }
        if (i <= midIndex) {
            paint.setColor(leftColor);
        } else {
            paint.setColor(rightColor);
        }
        paint.setStrokeWidth(barWidPx);
        float bh = (d / showMaxData) * viewHeight;
        bh = Math.max(bh, 4); // 最小也要一點高度 (1)
        float bhGap = (viewHeight - bh) / 2f;
        canvas.drawLine(x, bhGap, x, viewHeight - bhGap, paint);
    }

    drawMiddleLine(canvas);
}

private void drawMiddleLine(Canvas canvas) {
    paint.setColor(middleLineColor);
    canvas.drawLine(viewWid / 2f, 0, viewWid / 2f, viewHeight, paint);
}

如果數(shù)據(jù)太小，為了更美觀，也要顯示一點東西

左右拖動

本例給出的思路是在SoundWaveView中直接獲取觸摸事件并進行處理。

簡單區(qū)分一下模式，分為純展示和可拖動模式

/**
* 單純播放 展示 無交互
*/
public static final int MODE_PLAY = 1;

/**
* 允許左右拖動
*/
public static final int MODE_CAN_DRAG = 2;

復寫onTouchEvent方法，如果是MODE_CAN_DRAG模式，則攔截觸摸事件。判斷拖動的橫向（x）距離。

@Override
public boolean onTouchEvent(MotionEvent event) {
    if (mode == MODE_CAN_DRAG) {
        switch (event.getAction()) {
            case MotionEvent.ACTION_MOVE:
                float dx = (downX - event.getX()); // 不要那么靈敏
                float movePercent = dx / viewWid;
                int dIndex = (int) (movePercent * barCount);
                int targetMidIndex = downOldMidIndex + dIndex;
                targetMidIndex = Math.max(0, targetMidIndex);
                targetMidIndex = Math.min(targetMidIndex, dataList.size() - 1);
                setMidIndex(targetMidIndex);
                Log.d(TAG, "onTouchEvent-MOVE; dx: " + dx + ", dIndex: " + dIndex + "; targetMidIndex: " + targetMidIndex);
                break;
            case MotionEvent.ACTION_DOWN:
                downX = event.getX();
                downOldMidIndex = midIndex;
                break;
            case MotionEvent.ACTION_CANCEL:
            case MotionEvent.ACTION_UP:
                downOldMidIndex = midIndex;
                tellOnMoveEnd();
                break;
        }
        if (onEventListener != null) {
            onEventListener.onDragTouchEvent(event);
        }
        return true;
    }
    return super.onTouchEvent(event);
}

完整代碼

文件SoundWaveView.java，這個view主要目的是展現(xiàn)聲波，取名為「SoundWave」

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;

import androidx.annotation.Nullable;

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

/**
 * @author an.rustfisher.com
 */
public class SoundWaveView extends View {
    private static final String TAG = "rustAppSoundWaveView";

    /**
     * 單純播放 展示 無交互
     */
    public static final int MODE_PLAY = 1;

    /**
     * 允許左右拖動
     */
    public static final int MODE_CAN_DRAG = 2;

    private int mode = MODE_PLAY; // 1 播放
    private List<Float> dataList = new ArrayList<>(100);
    private float showMaxData = 40f; // 能顯示的最大數(shù)據(jù)
    private int midIndex = 0;   // 在中間顯示的數(shù)據(jù)的下標
    private float barWidDp = 1.5f;
    private float barWidPx = 3f;
    private float barGapPx = barWidPx / 2;
    private int barCount = 1;       // 當前寬度能繪制多少個柱子
    private int viewWid = 1000;     // px
    private int viewHeight = 100;   // px

    private final Paint paint = new Paint();
    private int leftColor = Color.GREEN;
    private int rightColor = Color.LTGRAY;
    private int middleLineColor = Color.parseColor("#55000000");

    private float downX = 0; // getX
    private int downOldMidIndex = 0;

    public interface OnEvent {
        void onMoveEnd(); // 停止拖動了

        void onDragTouchEvent(MotionEvent event);
    }

    private OnEvent onEventListener;

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

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

    public SoundWaveView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        paint.setColor(Color.BLUE);
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        viewWid = w;
        viewHeight = h;
        calBarPara();
        Log.d(TAG, "onSizeChanged: " + w + ", " + h);
        Log.d(TAG, "onSizeChanged: barWidPx: " + barWidPx);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        if (dataList == null || dataList.isEmpty()) {
            // draw nothing
            drawMiddleLine(canvas);
            return;
        }
        float x0 = viewWid / 2.0f;

        // 繪制數(shù)據(jù)
        if (midIndex > 0) {
            x0 = x0 - (barGapPx + barWidPx) * midIndex; // 可能是負數(shù)
        }
        for (int i = 0; i < dataList.size(); i++) {
            float d = dataList.get(i);
            float x = x0 + (barWidPx + barGapPx) * i;
            if (x < 0) {
                continue;
            }
            if (x > viewWid) {
                break;
            }
            if (i <= midIndex) {
                paint.setColor(leftColor);
            } else {
                paint.setColor(rightColor);
            }
            paint.setStrokeWidth(barWidPx);
            float bh = (d / showMaxData) * viewHeight;
            bh = Math.max(bh, 4); // 最小也要一點高度
            float bhGap = (viewHeight - bh) / 2f;
            canvas.drawLine(x, bhGap, x, viewHeight - bhGap, paint);
        }
        drawMiddleLine(canvas);
    }

    private void drawMiddleLine(Canvas canvas) {
        paint.setColor(middleLineColor);
        canvas.drawLine(viewWid / 2f, 0, viewWid / 2f, viewHeight, paint);
    }

    public float getMidByPercent() {
        return midIndex / (float) (dataList.size() - 1);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        if (mode == MODE_CAN_DRAG) {
            switch (event.getAction()) {
                case MotionEvent.ACTION_MOVE:
                    float dx = (downX - event.getX()); // 不要那么靈敏
                    float movePercent = dx / viewWid;
                    int dIndex = (int) (movePercent * barCount);
                    int targetMidIndex = downOldMidIndex + dIndex;
                    targetMidIndex = Math.max(0, targetMidIndex);
                    targetMidIndex = Math.min(targetMidIndex, dataList.size() - 1);
                    setMidIndex(targetMidIndex);
                    Log.d(TAG, "onTouchEvent-MOVE; dx: " + dx + ", dIndex: " + dIndex + "; targetMidIndex: " + targetMidIndex);
                    break;
                case MotionEvent.ACTION_DOWN:
                    downX = event.getX();
                    downOldMidIndex = midIndex;
                    break;
                case MotionEvent.ACTION_CANCEL:
                case MotionEvent.ACTION_UP:
                    downOldMidIndex = midIndex;
                    tellOnMoveEnd();
                    break;
            }
            if (onEventListener != null) {
                onEventListener.onDragTouchEvent(event);
            }
            return true;
        }
        return super.onTouchEvent(event);
    }

    public void setMode(int mode) {
        this.mode = mode;
    }

    public int getMode() {
        return mode;
    }

    public int getMidIndex() {
        return midIndex;
    }

    public List<Float> getDataList() {
        return dataList;
    }

    public void setOnEventListener(OnEvent onEventListener) {
        this.onEventListener = onEventListener;
    }

    public void clear() {
        dataList = new ArrayList<>();
        midIndex = 0;
        invalidate();
    }

    private void calBarPara() {
        barWidPx = dp2Px(barWidDp);
        barGapPx = barWidPx;
        barCount = (int) ((viewWid - barGapPx) / (barWidPx + barGapPx));
        paint.setStrokeWidth(barWidPx);
        Log.d(TAG, "calBarPara: barCount: " + barCount);
    }

    public void setDataList(List<Float> input) {
        dataList = new ArrayList<>(input);
        midIndex = 0;
        invalidate();
    }

    public void setMidIndex(int midIndex) {
        this.midIndex = midIndex;
        invalidate();
    }

    public void setMidEnd() {
        setMidIndex(dataList.size() - 1);
    }

    // 設(shè)置當前播放進度
    public void setPlayPercent(float percent) {
        midIndex = (int) (percent * (dataList.size() - 1));
        if (percent >= 1) {
            midIndex = dataList.size() - 1;
        }
        invalidate();
    }

    public void setShowMaxData(float showMaxData) {
        this.showMaxData = showMaxData;
    }

    public float getShowMaxData() {
        return showMaxData;
    }

    // 不停地插入數(shù)據(jù)
    public void addDataEnd(float f) {
        dataList.add(f);
        midIndex = dataList.size() - 1;
        invalidate();
    }

    public void setLeftColor(int leftColor) {
        this.leftColor = leftColor;
    }

    public void setRightColor(int rightColor) {
        this.rightColor = rightColor;
    }

    private float dp2Px(float dp) {
        float density = getContext().getResources().getDisplayMetrics().density;
        int mark = dp > 0 ? 1 : -1;
        return dp * density * mark;
    }

    private void tellOnMoveEnd() {
        if (onEventListener != null) {
            onEventListener.onMoveEnd();
        }
    }
}

layout中使用

<com.rustfisher.tutorial2020.customview.soundwave.SoundWaveView
    android:id="@+id/sound_wave_view"
    android:layout_width="match_parent"
    android:layout_height="100dp"
    android:layout_marginTop="4dp"
    android:background="@android:color/white"
    app:layout_constraintTop_toTopOf="parent" />

activity中使用模擬數(shù)據(jù)

private void setData1() {
    List<Float> dataList = new ArrayList<>();
    for (int i = 0; i < 1000; i++) {
        dataList.add((float) (Math.random() * soundWaveView.getShowMaxData()));
    }
    soundWaveView.setDataList(dataList);
    soundWaveView.setMidIndex(0);

    soundWaveView.setOnEventListener(new SoundWaveView.OnEvent() {
        @Override
        public void onMoveEnd() {
            Log.d(TAG, "onMoveEnd: " + soundWaveView.getMidIndex());
        }

        @Override
        public void onDragTouchEvent(MotionEvent event) {
            // 在這里可以收到觸摸事件
        }
    });
}

運行示例：