写一段Android 自定义柱状图代码

以下是一个简单的 Android 自定义柱状图的实现代码，使用 Canvas 和 Paint 绘制：

public class BarChartView extends View {
    private Paint mPaint;
    private List<Integer> mData;
    private int mMaxValue;
    private int mBarWidth;
    private int mBarColor;

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

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

        mPaint = new Paint();
        mPaint.setAntiAlias(true);

        TypedArray ta = context.obtainStyledAttributes(attrs, R.styleable.BarChartView);
        mBarWidth = ta.getDimensionPixelSize(R.styleable.BarChartView_bar_width, 20);
        mBarColor = ta.getColor(R.styleable.BarChartView_bar_color, Color.BLUE);
        ta.recycle();
    }

    public void setData(List<Integer> data) {
        mData = data;
        mMaxValue = Collections.max(mData);
        invalidate();
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);

        if (mData == null || mData.size() == 0) {
            return;
        }

        int width = getWidth();
        int height = getHeight();
        int barCount = mData.size();

        float startX = width / 2 - (barCount * mBarWidth) / 2;
        float startY = height - getPaddingBottom();

        mPaint.setColor(mBarColor);

        for (int i = 0; i < barCount; i++) {
            float barHeight = ((float) mData.get(i) / mMaxValue) * (height - getPaddingTop() - getPaddingBottom());
            canvas.drawRect(startX + i * mBarWidth, startY - barHeight, startX + (i + 1) * mBarWidth, startY, mPaint);
        }
    }
}

你可以在 XML 中添加该自定义 View：

<com.example.BarChartView
    android:id="@+id/bar_chart"
    android:layout_width="match_parent"
    android:layout_height="200dp"
    app:bar_width="30dp"
    app:bar_color="#FF4081" />

然后在代码中设置数据即可：

BarChartView barChart = findViewById(R.id.bar_chart);
List<Integer> data = Arrays.asList(5, 10, 15, 20, 25);
barChart.setData(data);