第一次写带图片的博客，多少还是有点紧张，效果不好，请将就着看，前面的图是今天要写的控件的效果图，元素不多，分别是一个按钮和一个自定义的控件。
在此以前，我看过许多的书，比如《Android群英传》、《第一行代码》等，也看了很多大神的博客，但是即便是这样，当我看到这么多代码的时候，一直都没有真正的动手去敲过这些代码，以至于我总是觉得自定义View是一个多么高深莫测的技术，我们这些小白是难以触及的，但是当昨晚看了一篇鸡汤之后，觉得人还是要学会专注，要耐得住寂寞，要沉得住气。所以在未来的几天，我也会持续的更新自己的博客，希望能够得到大家的监督，也希望能够一起成长。
一般来说，不到迫不得已，还是不要去自定义自己的控件，毕竟现在Android API已经给我提供了功能这么强大的控件了，而且你也能够发现，就算是这么强大的谷歌，很多控件也还是有自己的bug，更何况我们自己写的控件，当然了，通过自定义控件，来加深我们对Android系统的控件的了解，这也是进阶的一个好方法。好了，废话我先说到这里，下面开始今天的主题。
新建一个Class文件，命名为MyLineView，让它继承View，实现它的三个构造函数，紧接着初始化一些画笔、Path，圆等数据。代码如下：
1.定义变量
private Paint mPaint, mPaint2;
private Path mPath = new Path();
protected int mViewWidth, mViewHeight;
protected int mWidth, mHeight;
private float r, rArc, x;
private float percent = 0.5f;
private RectF rectF;
private PointF mPointF = new PointF(0, 0);
在构造函数里面初始化数据
public MyLineView(Context context, AttributeSet attrs) {
super(context, attrs);
mPaint = new Paint();
mPaint.setColor(Color.BLACK);
mPaint.setStrokeWidth(3);
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setTextSize(100);
mPaint2 = new Paint();
mPaint2.setColor(Color.CYAN);
mPaint2.setStrokeWidth(8);
mPaint2.setStyle(Paint.Style.FILL);
}
准备工作已经做好了，紧接着我们复写View的一个onSizeChanged()方法，故名思议，就是当控件的大小发生改变的时候调用。我们在这里对变量进行赋值，代码如下：
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
/**控件的高宽*/
mViewWidth = w;
mViewHeight = h;
/**与屏幕左边的距离和距离右边的距离*/
mWidth = mViewWidth - getPaddingLeft() - getPaddingRight();
mHeight = mViewHeight - getPaddingTop() - getPaddingBottom();
/**定义半径*/
r = Math.min(mWidth, mHeight) * 0.4f;
rectF = new RectF(-r, -r, r, r);
}
好了，这个时候的变量已经拥有值了，那可以开始写最重要的操作了，开始写onDraw();
@Override
protected void onDraw(Canvas canvas) {
// super.onDraw(canvas);
/** * 画曲线和外围的圆 */
canvas.translate(mViewWidth / 2, mViewHeight / 2);
canvas.drawCircle(0, 0, r, mPaint);
rArc = r * (1 - 2 * percent);
double angle = Math.acos((double) rArc / r);
x = r * (float) Math.sin(angle);
mPath.addArc(rectF, 90 - (float) Math.toDegrees(angle),
(float) Math.toDegrees(angle) * 2);
mPath.moveTo(-x, rArc);
mPath.rQuadTo(x / 2, -r / 8, x, 0);
mPath.rQuadTo(x / 2, r / 8, x, 0);
canvas.drawPath(mPath, mPaint2);
mPath.rewind();
/** * 画文字 */
NumberFormat numberFormat = NumberFormat.getPercentInstance();
numberFormat.setMinimumFractionDigits(1);
textCenter(new String[] { numberFormat.format(percent) }, mPaint,
canvas, mPointF, Paint.Align.CENTER);
}
文字的处理：
/** * 多行文本居中、居右、居左 * *@param strings * 文本字符串列表 *@param paint * 画笔 *@param canvas * 画布 *@param point * 点的坐标 *@param align * 居中、居右、居左 */
protected void textCenter(String[] strings, Paint paint, Canvas canvas,
PointF point, Paint.Align align) {
paint.setTextAlign(align);
Paint.FontMetrics fontMetrics = paint.getFontMetrics();
float top = fontMetrics.top;
float bottom = fontMetrics.bottom;
int length = strings.length;
float total = (length - 1) * (-top + bottom)
+ (-fontMetrics.ascent + fontMetrics.descent);
float offset = total / 2 - bottom;
for (int i = 0; i < length; i++) {
float yAxis = -(length - i - 1) * (-top + bottom) + offset;
canvas.drawText(strings[i], point.x, point.y + yAxis, paint);
}
}
好了，截止目前已经把控件写好了，但是作为一个控件，数据不可能固定不变，所以向外暴露一个方法，用于改变进度的大小；
public void setProgress(float percent) {
if (percent != 0) {
this.percent = percent;
} else {
this.percent = 0;
}
/**重绘*/
invalidate();
}
好了全部流程都在这里了，最后再贴上全部的代码；
package com.example.view.weight;
import java.text.NumberFormat;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.PointF;
import android.graphics.RectF;
import android.util.AttributeSet;
import android.view.View;
/** * 贝塞尔曲线 * *@author cheng * */
public class MyLineView extends View {
private Paint mPaint, mPaint2;
private Path mPath = new Path();
protected int mViewWidth, mViewHeight;
protected int mWidth, mHeight;
private float r, rArc, x;
private float percent = 0.5f;
private RectF rectF;
private PointF mPointF = new PointF(0, 0);
public MyLineView(Context context) {
this(context, null);
}
public MyLineView(Context context, AttributeSet attrs) {
super(context, attrs);
mPaint = new Paint();
mPaint.setColor(Color.BLACK);
mPaint.setStrokeWidth(3);
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setTextSize(100);
mPaint2 = new Paint();
mPaint2.setColor(Color.CYAN);
mPaint2.setStrokeWidth(8);
mPaint2.setStyle(Paint.Style.FILL);
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
mViewWidth = w;
mViewHeight = h;
mWidth = mViewWidth - getPaddingLeft() - getPaddingRight();
mHeight = mViewHeight - getPaddingTop() - getPaddingBottom();
r = Math.min(mWidth, mHeight) * 0.4f;
rectF = new RectF(-r, -r, r, r);
}
@Override
protected void onDraw(Canvas canvas) {
// super.onDraw(canvas);
/** * 画曲线和外围的圆 */
canvas.translate(mViewWidth / 2, mViewHeight / 2);
canvas.drawCircle(0, 0, r, mPaint);
rArc = r * (1 - 2 * percent);
double angle = Math.acos((double) rArc / r);
x = r * (float) Math.sin(angle);
mPath.addArc(rectF, 90 - (float) Math.toDegrees(angle),
(float) Math.toDegrees(angle) * 2);
mPath.moveTo(-x, rArc);
mPath.rQuadTo(x / 2, -r / 8, x, 0);
mPath.rQuadTo(x / 2, r / 8, x, 0);
canvas.drawPath(mPath, mPaint2);
mPath.rewind();
/** * 画文字 */
NumberFormat numberFormat = NumberFormat.getPercentInstance();
numberFormat.setMinimumFractionDigits(1);
textCenter(new String[] { numberFormat.format(percent) }, mPaint,
canvas, mPointF, Paint.Align.CENTER);
}
/** * 多行文本居中、居右、居左 * *@param strings * 文本字符串列表 *@param paint * 画笔 *@param canvas * 画布 *@param point * 点的坐标 *@param align * 居中、居右、居左 */
protected void textCenter(String[] strings, Paint paint, Canvas canvas,
PointF point, Paint.Align align) {
paint.setTextAlign(align);
Paint.FontMetrics fontMetrics = paint.getFontMetrics();
float top = fontMetrics.top;
float bottom = fontMetrics.bottom;
int length = strings.length;
float total = (length - 1) * (-top + bottom)
+ (-fontMetrics.ascent + fontMetrics.descent);
float offset = total / 2 - bottom;
for (int i = 0; i < length; i++) {
float yAxis = -(length - i - 1) * (-top + bottom) + offset;
canvas.drawText(strings[i], point.x, point.y + yAxis, paint);
}
}
public void setProgress(float percent) {
if (percent != 0) {
this.percent = percent;
} else {
this.percent = 0;
}
invalidate();
}
}
布局里面的代码：
android:id="@+id/view_line"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:gravity="center" />
