自定义View小心得

最近一直想学习一下Android自定义View的编写。

所以在网上找了很多源码来研究，在此特别感谢Android巴士和GitHub能为我们提供如此多的Android开发源码。在此我就一最近下载的一个项目为例，讲讲自定义控件源码下载地址：http://www.apkbus.com/forum.php?mod=viewthread&tid=243738，在此再次感谢作者的无私贡献。运行效果图参考： http://data.apkbus.com/3p15535534AU913。

首先给自定义View 定义自己的属性，在Res/Values 文件夹下创建attrs.xml资源文件

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <declare-styleable name="NumberProgressBar">
        <!-- 进度值 -->
        <attr name="progress_current" format="integer"/>
       <!--  进度条最大值 -->
        <attr name="progress_max" format="integer"/>
       <!--进度条未加载的背景色 -->
        <attr name="progress_unreached_color" format="color"/>
         <!-- 进度条加载的背景色 -->
        <attr name="progress_reached_color" format="color"/>

        <!--  进度条的高 -->
        <attr name="progress_reached_bar_height" format="dimension"/>
        <attr name="progress_unreached_bar_height" format="dimension"/>

        <!--  进度条的提示进度字体大小和颜色 -->
        <attr name="progress_text_size" format="dimension"/>
        <attr name="progress_text_color" format="color"/>

        <attr name="progress_text_offset" format="dimension"/>
          <!-- 进度条的提示进度文字是否可见 -->
        <attr name="progress_text_visibility" format="enum">
            <enum name="visible" value="0"/>
            <enum name="invisible" value="1"/>
        </attr>
    </declare-styleable>

</resources>

自定义控件的基本属性定义好了以后，下面开始实现进度条的改变的接口以便扩展自定义控件的功能。

public interface OnProgressBarListener {
   // 进度条值改变的监听
    void onProgressChange(int current, int max);
}

下一步开始编写自定义控件，代码如下，因为篇幅问题部分代码省略，只是重点讲解一下编写思路，想看源码的可以自己下载：

/**
 * Created by daimajia on 14-4-30.
 */
public class NumberProgressBar extends View {
    /**
     * Listener
     */
    private OnProgressBarListener mListener;

    public enum ProgressTextVisibility {
        Visible, Invisible
    }

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

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


        //load styled attributes.通过TypedArray 获取控件的属性
         TypedArray attributes = context.obtainStyledAttributes(attrs, R.styleable.NumberProgressBar);

        mReachedBarColor = attributes.getColor(R.styleable.NumberProgressBar_progress_reached_color, default_reached_color);
        mUnreachedBarColor = attributes.getColor(R.styleable.NumberProgressBar_progress_unreached_color, default_unreached_color);
        mTextColor = attributes.getColor(R.styleable.NumberProgressBar_progress_text_color, default_text_color);
        mTextSize = attributes.getDimension(R.styleable.NumberProgressBar_progress_text_size, default_text_size);
        mReachedBarHeight = attributes.getDimension(R.styleable.NumberProgressBar_progress_reached_bar_height, default_reached_bar_height);
        mUnreachedBarHeight = attributes.getDimension(R.styleable.NumberProgressBar_progress_unreached_bar_height, default_unreached_bar_height);
        mOffset = attributes.getDimension(R.styleable.NumberProgressBar_progress_text_offset, default_progress_text_offset);

        int textVisible = attributes.getInt(R.styleable.NumberProgressBar_progress_text_visibility, PROGRESS_TEXT_VISIBLE);
        if (textVisible != PROGRESS_TEXT_VISIBLE) {
            mIfDrawText = false;
        }

        setProgress(attributes.getInt(R.styleable.NumberProgressBar_progress_current, 0));
        setMax(attributes.getInt(R.styleable.NumberProgressBar_progress_max, 100));
	//attributes 回收
        attributes.recycle();
	//初始化画笔，用于绘制界面
        initializePainters();
    }



    @Override
    protected int getSuggestedMinimumWidth() {
        return (int) mTextSize;
    }

    @Override
    protected int getSuggestedMinimumHeight() {
        return Math.max((int) mTextSize, Math.max((int) mReachedBarHeight, (int) mUnreachedBarHeight));
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
       //测量控件的大小 ，然后绘制
        setMeasuredDimension(measure(widthMeasureSpec, true), measure(heightMeasureSpec, false));
    }

    private int measure(int measureSpec, boolean isWidth) {
        int result;
        int mode = MeasureSpec.getMode(measureSpec);
        int size = MeasureSpec.getSize(measureSpec);
        int padding = isWidth ? getPaddingLeft() + getPaddingRight() : getPaddingTop() + getPaddingBottom();
        if (mode == MeasureSpec.EXACTLY) {
            result = size;
        } else {
            result = isWidth ? getSuggestedMinimumWidth() : getSuggestedMinimumHeight();
            result += padding;
            if (mode == MeasureSpec.AT_MOST) {
                if (isWidth) {
                    result = Math.max(result, size);
                } else {
                    result = Math.min(result, size);
                }
            }
        }
        return result;
    }

  //绘制控件
    @Override
    protected void onDraw(Canvas canvas) {
        if (mIfDrawText) {
            calculateDrawRectF();
        } else {
            calculateDrawRectFWithoutProgressText();
        }

        if (mDrawReachedBar) {
            canvas.drawRect(mReachedRectF, mReachedBarPaint);
        }

        if (mDrawUnreachedBar) {
            canvas.drawRect(mUnreachedRectF, mUnreachedBarPaint);
        }
	//判断是否绘制提示文字
        if (mIfDrawText)
            canvas.drawText(mCurrentDrawText, mDrawTextStart, mDrawTextEnd, mTextPaint);
    }

    //初始化画笔，用于绘制 自定义控件的进度条加载颜色 未加载颜色和 显示字体颜色
    private void initializePainters() {
        mReachedBarPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
        mReachedBarPaint.setColor(mReachedBarColor);

        mUnreachedBarPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
        mUnreachedBarPaint.setColor(mUnreachedBarColor);

        mTextPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
        mTextPaint.setColor(mTextColor);
        mTextPaint.setTextSize(mTextSize);
    }

	//计算提示文字隐藏的 矩形背景位置
    private void calculateDrawRectFWithoutProgressText() {
        mReachedRectF.left = getPaddingLeft();
        mReachedRectF.top = getHeight() / 2.0f - mReachedBarHeight / 2.0f;
        mReachedRectF.right = (getWidth() - getPaddingLeft() - getPaddingRight()) / (getMax() * 1.0f) * getProgress() + getPaddingLeft();
        mReachedRectF.bottom = getHeight() / 2.0f + mReachedBarHeight / 2.0f;

        mUnreachedRectF.left = mReachedRectF.right;
        mUnreachedRectF.right = getWidth() - getPaddingRight();
        mUnreachedRectF.top = getHeight() / 2.0f + -mUnreachedBarHeight / 2.0f;
        mUnreachedRectF.bottom = getHeight() / 2.0f + mUnreachedBarHeight / 2.0f;
    }

	//计算提示文字没有隐藏的 矩形背景位置
    private void calculateDrawRectF() {

        mCurrentDrawText = String.format("%d", getProgress() * 100 / getMax());
        mCurrentDrawText = mPrefix + mCurrentDrawText + mSuffix;
        mDrawTextWidth = mTextPaint.measureText(mCurrentDrawText);

        if (getProgress() == 0) {
            mDrawReachedBar = false;
            mDrawTextStart = getPaddingLeft();
        } else {
            mDrawReachedBar = true;
            mReachedRectF.left = getPaddingLeft();
            mReachedRectF.top = getHeight() / 2.0f - mReachedBarHeight / 2.0f;
            mReachedRectF.right = (getWidth() - getPaddingLeft() - getPaddingRight()) / (getMax() * 1.0f) * getProgress() - mOffset + getPaddingLeft();
            mReachedRectF.bottom = getHeight() / 2.0f + mReachedBarHeight / 2.0f;
            mDrawTextStart = (mReachedRectF.right + mOffset);
        }

        mDrawTextEnd = (int) ((getHeight() / 2.0f) - ((mTextPaint.descent() + mTextPaint.ascent()) / 2.0f));

        if ((mDrawTextStart + mDrawTextWidth) >= getWidth() - getPaddingRight()) {
            mDrawTextStart = getWidth() - getPaddingRight() - mDrawTextWidth;
            mReachedRectF.right = mDrawTextStart - mOffset;
        }

        float unreachedBarStart = mDrawTextStart + mDrawTextWidth + mOffset;
        if (unreachedBarStart >= getWidth() - getPaddingRight()) {
            mDrawUnreachedBar = false;
        } else {
            mDrawUnreachedBar = true;
            mUnreachedRectF.left = unreachedBarStart;
            mUnreachedRectF.right = getWidth() - getPaddingRight();
            mUnreachedRectF.top = getHeight() / 2.0f + -mUnreachedBarHeight / 2.0f;
            mUnreachedRectF.bottom = getHeight() / 2.0f + mUnreachedBarHeight / 2.0f;
        }
    }


// 设置进度条的进度
   public void setProgress(int progress) {
        if (progress <= getMax() && progress >= 0) {
            this.mCurrentProgress = progress;
           // 更新Ui
            invalidate();
        }
    }

    
//现场保护机智 想了解的自己百度哈
    @Override
    protected Parcelable onSaveInstanceState() {
        final Bundle bundle = new Bundle();
        bundle.putParcelable(INSTANCE_STATE, super.onSaveInstanceState());
        bundle.putInt(INSTANCE_TEXT_COLOR, getTextColor());
        bundle.putFloat(INSTANCE_TEXT_SIZE, getProgressTextSize());
        bundle.putFloat(INSTANCE_REACHED_BAR_HEIGHT, getReachedBarHeight());
        bundle.putFloat(INSTANCE_UNREACHED_BAR_HEIGHT, getUnreachedBarHeight());
        bundle.putInt(INSTANCE_REACHED_BAR_COLOR, getReachedBarColor());
        bundle.putInt(INSTANCE_UNREACHED_BAR_COLOR, getUnreachedBarColor());
        bundle.putInt(INSTANCE_MAX, getMax());
        bundle.putInt(INSTANCE_PROGRESS, getProgress());
        bundle.putString(INSTANCE_SUFFIX, getSuffix());
        bundle.putString(INSTANCE_PREFIX, getPrefix());
        bundle.putBoolean(INSTANCE_TEXT_VISIBILITY, getProgressTextVisibility());
        return bundle;
    }

    @Override
    protected void onRestoreInstanceState(Parcelable state) {
        if (state instanceof Bundle) {
            final Bundle bundle = (Bundle) state;
            mTextColor = bundle.getInt(INSTANCE_TEXT_COLOR);
            mTextSize = bundle.getFloat(INSTANCE_TEXT_SIZE);
            mReachedBarHeight = bundle.getFloat(INSTANCE_REACHED_BAR_HEIGHT);
            mUnreachedBarHeight = bundle.getFloat(INSTANCE_UNREACHED_BAR_HEIGHT);
            mReachedBarColor = bundle.getInt(INSTANCE_REACHED_BAR_COLOR);
            mUnreachedBarColor = bundle.getInt(INSTANCE_UNREACHED_BAR_COLOR);
            initializePainters();
            setMax(bundle.getInt(INSTANCE_MAX));
            setProgress(bundle.getInt(INSTANCE_PROGRESS));
            setPrefix(bundle.getString(INSTANCE_PREFIX));
            setSuffix(bundle.getString(INSTANCE_SUFFIX));
            setProgressTextVisibility(bundle.getBoolean(INSTANCE_TEXT_VISIBILITY) ? Visible : Invisible);
            super.onRestoreInstanceState(bundle.getParcelable(INSTANCE_STATE));
            return;
        }
        super.onRestoreInstanceState(state);
    }


}

自定义控件的几个步骤：可以参考http://www.cnblogs.com/purediy/p/3799534.html

下面简单做个总结：其实本人做开发也才半年左右，这次是我第一次写博客与大家分享，希望大家多多支持，有写的不好的地方希望大家不吝赐教。

只要大家一起努力一定会有所收获的，最后感谢哪些在网上无私分享学习心得和源码的大神，愿好人一身平安。

自定义View小心得

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