Android自己定义视图（一）：带下划线的TextView

package com.francis.underlinetextviewtest;

import android.content.Context;
import android.content.res.Resources;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.util.Log;
import android.util.TypedValue;
import android.widget.TextView;

/**
 * Created by Francis on 14-10-13.
 */
public class UnderlineTextView extends TextView {

    private final Paint mPaint = new Paint();
    private int mUnderlineHeight = 0;

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

    public UnderlineTextView(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public UnderlineTextView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        init(context, attrs);
    }

    private void init(Context context, AttributeSet attrs) {
        Resources r = getResources();
        // mUnderlineHeight == 6
        mUnderlineHeight = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 2, r.getDisplayMetrics());
    }

    @Override
    public void setPadding(int left, int top, int right, int bottom) {
        super.setPadding(left, top, right, bottom + mUnderlineHeight);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        // Draw the underline the same color as the text

        mPaint.setColor(getTextColors().getDefaultColor());
        // 对角线上的两点。

canvas.drawRect(0, getHeight() - mUnderlineHeight, getWidth(), getHeight(), mPaint);
    }
}

加入布局文件：

<com.francis.underlinetextviewtest.UnderlineTextView
        android:text="@string/hello_world"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textStyle="bold"
        android:textColor="#FFDDDDDD"/>