Android自定义控件

<?xml version="1.0" encoding="utf-8"?>
<resources>

    <declare-styleable name="PieChart">
        <attr name="showText" format="boolean" />
        <attr name="textSize" format="dimension"></attr>
        <attr name="contentText" format="string"></attr>
    </declare-styleable>

</resources>

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:custom="http://schemas.android.com/apk/res/com.example.customview"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.customview.MainActivity" >

    <com.example.customview.view.PieChart
        android:layout_width="250dp"
        android:layout_height="250dp"
        android:layout_centerInParent="true"
        android:background="@android:color/holo_blue_light"
        custom:contentText="你好"
        custom:showText="true"
        custom:textSize="50sp" />

</RelativeLayout>

private boolean mShowText;
private int mTextSize;
private String mContentText;

public PieChart(Context context, AttributeSet attrs) {
        super(context, attrs);
        TypedArray a = context.getTheme().obtainStyledAttributes(attrs,
                R.styleable.PieChart, 0, 0);

        try {
            mShowText = a.getBoolean(R.styleable.PieChart_showText, false);
            // mTextSize = a.getInteger(R.styleable.PieChart_textSize,12);这是错误的获取方式
            mTextSize = a.getDimensionPixelSize(R.styleable.PieChart_textSize,
                    (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP,
                            12, getResources().getDisplayMetrics()));
            mContentText = a.getString(R.styleable.PieChart_contentText);
        } finally {
            a.recycle();
        }
        init();
    }

private Paint mTextPaint;
private Rect mBound;

private void init() {
        mTextPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
        mTextPaint.setTextSize(mTextSize);
        mTextPaint.setStyle(Paint.Style.FILL);
        mTextPaint.setColor(0xff101010);
        mBound = new Rect();
        mTextPaint
                .getTextBounds(mContentText, 0, mContentText.length(), mBound);

    }

public boolean isShowText() {
   return mShowText;
}
 
public void setShowText(boolean showText) {
   mShowText = showText;
   invalidate();
   requestLayout();
}

@Override
    protected void onDraw(Canvas canvas) {
        // TODO Auto-generated method stub
        super.onDraw(canvas);
        if (mShowText)//根据我们获取的设置的自定义属性，判断是否显示文本
            canvas.drawText(mContentText, getWidth() / 2 - mBound.width() / 2,
                    getHeight() / 2 + mBound.height() / 2, mTextPaint);
        //getWidth() / 2 - mBound.width() / 2,getHeight() / 2 + mBound.height() / 2
        //这是为了使文本居中
        else
            canvas.drawText("内容为空", getWidth() / 2 - mBound.width() / 2,
                    getHeight() / 2 + mBound.height() / 2, mTextPaint);

    }

@Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        setMeasuredDimension(measureWidth(widthMeasureSpec),
                measureHeight(heightMeasureSpec));
    }

/**
     * Determines the width of this view
     * 
     * @param measureSpec
     *            A measureSpec packed into an int
     * @return The width of the view, honoring constraints from measureSpec
     */
    private int measureWidth(int measureSpec) {
        int result = 0;
        int specMode = MeasureSpec.getMode(measureSpec);
        int specSize = MeasureSpec.getSize(measureSpec);

        if (specMode == MeasureSpec.EXACTLY) {
            // We were told how big to be
            result = specSize;
        } else {
            // Measure the text
            result = (int) mTextPaint.measureText(mContentText)
                    + getPaddingLeft() + getPaddingRight();
            if (specMode == MeasureSpec.AT_MOST) {
                // Respect AT_MOST value if that was what is called for by
                // measureSpec
                result = Math.min(result, specSize);
            }
        }

        return result;
    }

private int mAscent;

/**
     * Determines the height of this view
     * 
     * @param measureSpec
     *            A measureSpec packed into an int
     * @return The height of the view, honoring constraints from measureSpec
     */
    private int measureHeight(int measureSpec) {
        int result = 0;
        int specMode = MeasureSpec.getMode(measureSpec);
        int specSize = MeasureSpec.getSize(measureSpec);

        mAscent = (int) mTextPaint.ascent();
        if (specMode == MeasureSpec.EXACTLY) {
            // We were told how big to be
            result = specSize;
        } else {
            // Measure the text (beware: ascent is a negative number)
            result = (int) (-mAscent + mTextPaint.descent()) + getPaddingTop()
                    + getPaddingBottom();
            if (specMode == MeasureSpec.AT_MOST) {
                // Respect AT_MOST value if that was what is called for by
                // measureSpec
                result = Math.min(result, specSize);
            }
        }
        return result;
    }