转载请标明出处：http://blog.csdn.net/lmj623565791/article/details/46695347；本文出自:【张鸿洋的博客】一、概述周末游戏打得过猛，于是周天熬夜码代码，周一早上浑浑噩噩的发现android-percent-support-lib-sample这个项目，Google终于开始支持百分比的方式布局了，瞬间脉动回来，啊咧咧。对于这种历史性的时刻，不出篇博客难以表达我内心的激动。还记得不久前，发了篇博客：Android 屏幕适配方案，这篇博客以Web页面设计引出一种适配方案，最终的目的就是可以通过百分比控制控件的大小。当然了，存在一些问题，比如：对于没有考虑到屏幕尺寸，可能会出现意外的情况；apk的大小会增加；当然了android-percent-support这个库，基本可以解决上述问题，是不是有点小激动，稍等，我们先描述下这个support-lib。这个库提供了：两种布局供大家使用：PercentRelativeLayout、PercentFrameLayout，通过名字就可以看出，这是继承自FrameLayout和RelativeLayout两个容器类；支持的属性有：layout_widthPercent、layout_heightPercent、layout_marginPercent、layout_marginLeftPercent、layout_marginTopPercent、layout_marginRightPercent、layout_marginBottomPercent、layout_marginStartPercent、layout_marginEndPercent。可以看到支持宽高，以及margin。也就是说，大家只要在开发过程中使用PercentRelativeLayout、PercentFrameLayout替换FrameLayout、RelativeLayout即可。是不是很简单，不过貌似没有LinearLayout，有人会说LinearLayout有weight属性呀。但是，weight属性只能支持一个方向呀~~哈，没事，刚好给我们一个机会去自定义一个PercentLinearLayout。好了，本文分为3个部分：PercentRelativeLayout、PercentFrameLayout的使用对上述控件源码分析自定义PercentLinearLayout二、使用关于使用，其实及其简单，并且github上也有例子，android-percent-support-lib-sample。我们就简单过一下：首先记得在build.gradle添加：compile 'com.android.support:percent:22.2.0'（一）PercentFrameLayout
3个TextView，很简单，直接看效果图：(二) PercentRelativeLayoutok，依然是直接看效果图:使用没什么好说的，就是直观的看一下。三、源码分析其实细想一下，Google只是对我们原本熟悉的RelativeLayout和FrameLayout进行的功能的扩展，使其支持了percent相关的属性。那么，我们考虑下，如果是我们添加这种扩展，我们会怎么做：通过LayoutParams获取child设置的percent相关属性的值onMeasure的时候，将child的width,height的值，通过获取的自定义属性的值进行计算（eg:容器的宽 * fraction ），计算后传入给child.measure(w,h);ok，有了上面的猜想，我们直接看PercentFrameLayout的源码。publicclassPercentFrameLayoutextendsFrameLayout{privatefinalPercentLayoutHelper mHelper =newPercentLayoutHelper(this);//省略了，两个构造方法publicPercentFrameLayout(Context context, AttributeSet attrs) {super(context, attrs);
}@OverridepublicLayoutParamsgenerateLayoutParams(AttributeSet attrs) {returnnewLayoutParams(getContext(), attrs);
}@OverrideprotectedvoidonMeasure(intwidthMeasureSpec,intheightMeasureSpec) {
mHelper.adjustChildren(widthMeasureSpec, heightMeasureSpec);super.onMeasure(widthMeasureSpec, heightMeasureSpec);if(mHelper.handleMeasuredStateTooSmall()) {super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}
}@OverrideprotectedvoidonLayout(booleanchanged,intleft,inttop,intright,intbottom) {super.onLayout(changed, left, top, right, bottom);
mHelper.restoreOriginalParams();
}publicstaticclassLayoutParamsextendsFrameLayout.LayoutParamsimplementsPercentLayoutHelper.PercentLayoutParams{privatePercentLayoutHelper.PercentLayoutInfo mPercentLayoutInfo;publicLayoutParams(Context c, AttributeSet attrs) {super(c, attrs);
mPercentLayoutInfo = PercentLayoutHelper.getPercentLayoutInfo(c, attrs);
}//省略了一些代码...@OverridepublicPercentLayoutHelper.PercentLayoutInfogetPercentLayoutInfo() {returnmPercentLayoutInfo;
}@OverrideprotectedvoidsetBaseAttributes(TypedArray a,intwidthAttr,intheightAttr) {
PercentLayoutHelper.fetchWidthAndHeight(this, a, widthAttr, heightAttr);
}
}
}代码是相当的短，可以看到PercentFrameLayout里面首先重写了generateLayoutParams方法，当然了，由于支持了一些新的layout_属性，那么肯定需要定义对应的LayoutParams。（一）percent相关属性的获取可以看到PercentFrameLayout.LayoutParams在原有的FrameLayout.LayoutParams基础上，实现了PercentLayoutHelper.PercentLayoutParams接口。这个接口很简单，只有一个方法：publicinterfacePercentLayoutParams{PercentLayoutInfo getPercentLayoutInfo();
}而，这个方法的实现呢，也只有一行：return mPercentLayoutInfo;，那么这个mPercentLayoutInfo在哪完成赋值呢？看PercentFrameLayout.LayoutParams的构造方法：publicLayoutParams(Context c, AttributeSet attrs) {super(c, attrs);
mPercentLayoutInfo = PercentLayoutHelper.getPercentLayoutInfo(c, attrs);
}可以看到，将attrs传入给getPercentLayoutInfo方法，那么不用说，这个方法的内部，肯定是获取自定义属性的值，然后将其封装到PercentLayoutInfo对象中，最后返回。代码如下：publicstaticPercentLayoutInfogetPercentLayoutInfo(Context context,
AttributeSet attrs) {
PercentLayoutInfo info =null;
TypedArray array = context.obtainStyledAttributes(attrs, R.styleable.PercentLayout_Layout);floatvalue = array.getFraction(R.styleable.PercentLayout_Layout_layout_widthPercent,1,1,
-1f);if(value != -1f) {if(Log.isLoggable(TAG, Log.VERBOSE)) {
Log.v(TAG,"percent width: "+ value);
}
info = info !=null? info :newPercentLayoutInfo();
info.widthPercent = value;
}
value = array.getFraction(R.styleable.PercentLayout_Layout_layout_heightPercent,1,1, -1f);if(value != -1f) {if(Log.isLoggable(TAG, Log.VERBOSE)) {
Log.v(TAG,"percent height: "+ value);
}
info = info !=null? info :newPercentLayoutInfo();
info.heightPercent = value;
}
value = array.getFraction(R.styleable.PercentLayout_Layout_layout_marginPercent,1,1, -1f);if(value != -1f) {if(Log.isLoggable(TAG, Log.VERBOSE)) {
Log.v(TAG,"percent margin: "+ value);
}
info = info !=null? info :newPercentLayoutInfo();
info.leftMarginPercent = value;
info.topMarginPercent = value;
info.rightMarginPercent = value;
info.bottomMarginPercent = value;
}
value = array.getFraction(R.styleable.PercentLayout_Layout_layout_marginLeftPercent,1,1,
-1f);if(value != -1f) {if(Log.isLoggable(TAG, Log.VERBOSE)) {
Log.v(TAG,"percent left margin: "+ value);
}
info = info !=null? info :newPercentLayoutInfo();
info.leftMarginPercent = value;
}
value = array.getFraction(R.styleable.PercentLayout_Layout_layout_marginTopPercent,1,1,
-1f);if(value != -1f) {if(Log.isLoggable(TAG, Log.VERBOSE)) {
Log.v(TAG,"percent top margin: "+ value);
}
info = info !=null? info :newPercentLayoutInfo();
info.topMarginPercent = value;
}
value = array.getFraction(R.styleable.PercentLayout_Layout_layout_marginRightPercent,1,1,
-1f);if(value != -1f) {if(Log.isLoggable(TAG, Log.VERBOSE)) {
Log.v(TAG,"percent right margin: "+ value);
}
info = info !=null? info :newPercentLayoutInfo();
info.rightMarginPercent = value;
}
value = array.getFraction(R.styleable.PercentLayout_Layout_layout_marginBottomPercent,1,1,
-1f);if(value != -1f) {if(Log.isLoggable(TAG, Log.VERBOSE)) {
Log.v(TAG,"percent bottom margin: "+ value);
}
info = info !=null? info :newPercentLayoutInfo();
info.bottomMarginPercent = value;
}
value = array.getFraction(R.styleable.PercentLayout_Layout_layout_marginStartPercent,1,1,
-1f);if(value != -1f) {if(Log.isLoggable(TAG, Log.VERBOSE)) {
Log.v(TAG,"percent start margin: "+ value);
}
info = info !=null? info :newPercentLayoutInfo();
info.startMarginPercent = value;
}
value = array.getFraction(R.styleable.PercentLayout_Layout_layout_marginEndPercent,1,1,
-1f);if(value != -1f) {if(Log.isLoggable(TAG, Log.VERBOSE)) {
Log.v(TAG,"percent end margin: "+ value);
}
info = info !=null? info :newPercentLayoutInfo();
info.endMarginPercent = value;
}
array.recycle();if(Log.isLoggable(TAG, Log.DEBUG)) {
Log.d(TAG,"constructed: "+ info);
}returninfo;
}是不是和我们平时的取值很类似，所有的值最终封装到PercentLayoutInfo对象中。ok，到此我们的属性获取就介绍完成，有了这些属性，是不是onMeasure里面要进行使用呢？(二) onMeasue中重新计算child的尺寸@OverrideprotectedvoidonMeasure(intwidthMeasureSpec,intheightMeasureSpec) {
mHelper.adjustChildren(widthMeasureSpec, heightMeasureSpec);super.onMeasure(widthMeasureSpec, heightMeasureSpec);if(mHelper.handleMeasuredStateTooSmall()) {super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}
}可以看到onMeasure中的代码页很少，看来核心的代码都被封装在mHelper的方法中，我们直接看mHelper.adjustChildren方法。/**
* Iterates over children and changes their width and height to one calculated from percentage
* values.
*@paramwidthMeasureSpec Width MeasureSpec of the parent ViewGroup.
*@paramheightMeasureSpec Height MeasureSpec of the parent ViewGroup.
*/publicvoidadjustChildren(intwidthMeasureSpec,intheightMeasureSpec) {//...intwidthHint = View.MeasureSpec.getSize(widthMeasureSpec);intheightHint = View.MeasureSpec.getSize(heightMeasureSpec);for(inti =0, N = mHost.getChildCount(); i < N; i++) {
View view = mHost.getChildAt(i);
ViewGroup.LayoutParams params = view.getLayoutParams();if(paramsinstanceofPercentLayoutParams) {
PercentLayoutInfo info =
((PercentLayoutParams) params).getPercentLayoutInfo();if(Log.isLoggable(TAG, Log.DEBUG)) {
Log.d(TAG,"using "+ info);
}if(info !=null) {if(paramsinstanceofViewGroup.MarginLayoutParams) {
info.fillMarginLayoutParams((ViewGroup.MarginLayoutParams) params,
widthHint, heightHint);
}else{
info.fillLayoutParams(params, widthHint, heightHint);
}
}
}
}
}通过注释也能看出，此方法中遍历所有的孩子，通过百分比的属性重新设置其宽度和高度。首先在widthHint、heightHint保存容器的宽、高，然后遍历所有的孩子，判断其LayoutParams是否是PercentLayoutParams类型，如果是，通过params.getPercentLayoutInfo拿出info对象。是否还记得，上面的分析中，PercentLayoutInfo保存了percent相关属性的值。如果info不为null，则判断是否需要处理margin；我们直接看fillLayoutParams方法（处理margin也是类似的）。/**
* Fills {@code ViewGroup.LayoutParams} dimensions based on percentage values.
*/publicvoidfillLayoutParams(ViewGroup.LayoutParams params,intwidthHint,intheightHint) {// Preserve the original layout params, so we can restore them after the measure step.mPreservedParams.width = params.width;
mPreservedParams.height = params.height;if(widthPercent >=0) {
params.width = (int) (widthHint * widthPercent);
}if(heightPercent >=0) {
params.height = (int) (heightHint * heightPercent);
}if(Log.isLoggable(TAG, Log.DEBUG)) {
Log.d(TAG,"after fillLayoutParams: ("+ params.width +", "+ params.height +")");
}
}首先保存原本的width和height，然后重置params的width和height为(int) (widthHint * widthPercent)和(int) (heightHint * heightPercent);。到此，其实我们的百分比转换就结束了，理论上就已经实现了对于百分比的支持，不过Google还考虑了一些细节。我们回到onMeasure方法：@OverrideprotectedvoidonMeasure(intwidthMeasureSpec,intheightMeasureSpec) {
mHelper.adjustChildren(widthMeasureSpec, heightMeasureSpec);super.onMeasure(widthMeasureSpec, heightMeasureSpec);if(mHelper.handleMeasuredStateTooSmall()) {super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}
}下面还有个mHelper.handleMeasuredStateTooSmall的判断，也就是说，如果你设置的百分比，最终计算出来的MeasuredSize过小的话，会进行一些操作。代码如下：publicbooleanhandleMeasuredStateTooSmall() {booleanneedsSecondMeasure =false;for(inti =0, N = mHost.getChildCount(); i < N; i++) {
View view = mHost.getChildAt(i);
ViewGroup.LayoutParams params = view.getLayoutParams();if(Log.isLoggable(TAG, Log.DEBUG)) {
Log.d(TAG,"should handle measured state too small "+ view +" "+ params);
}if(paramsinstanceofPercentLayoutParams) {
PercentLayoutInfo info =
((PercentLayoutParams) params).getPercentLayoutInfo();if(info !=null) {if(shouldHandleMeasuredWidthTooSmall(view, info)) {
needsSecondMeasure =true;
params.width = ViewGroup.LayoutParams.WRAP_CONTENT;
}if(shouldHandleMeasuredHeightTooSmall(view, info)) {
needsSecondMeasure =true;
params.height = ViewGroup.LayoutParams.WRAP_CONTENT;
}
}
}
}if(Log.isLoggable(TAG, Log.DEBUG)) {
Log.d(TAG,"should trigger second measure pass: "+ needsSecondMeasure);
}returnneedsSecondMeasure;
}首先遍历所有的孩子，拿出孩子的layoutparams，如果是PercentLayoutParams实例，则取出info。如果info不为null，调用shouldHandleMeasuredWidthTooSmall判断：privatestaticbooleanshouldHandleMeasuredWidthTooSmall(View view, PercentLayoutInfo info) {intstate = ViewCompat.getMeasuredWidthAndState(view) & ViewCompat.MEASURED_STATE_MASK;returnstate == ViewCompat.MEASURED_STATE_TOO_SMALL && info.widthPercent >=0&&
info.mPreservedParams.width == ViewGroup.LayoutParams.WRAP_CONTENT;
}这里就是判断，如果你设置的measuredWidth或者measureHeight过小的话，并且你在布局文件中layout_w/h 设置的是WRAP_CONTENT的话，将params.width / height= ViewGroup.LayoutParams.WRAP_CONTENT，然后重新测量。哈，onMeasure终于结束了~~~现在我觉得应该代码结束了吧，尺寸都设置好了，还需要干嘛么，but，你会发现onLayout也重写了，我们又不改变layout规则，在onLayout里面干什么毛线：@OverrideprotectedvoidonLayout(booleanchanged,intleft,inttop,intright,intbottom) {super.onLayout(changed, left, top, right, bottom);
mHelper.restoreOriginalParams();
}继续看mHelper.restoreOriginalParams/**
* Iterates over children and restores their original dimensions that were changed for
* percentage values. Calling this method only makes sense if you previously called
* {@link PercentLayoutHelper#adjustChildren(int, int)}.
*/publicvoidrestoreOriginalParams() {for(inti =0, N = mHost.getChildCount(); i < N; i++) {
View view = mHost.getChildAt(i);
ViewGroup.LayoutParams params = view.getLayoutParams();if(Log.isLoggable(TAG, Log.DEBUG)) {
Log.d(TAG,"should restore "+ view +" "+ params);
}if(paramsinstanceofPercentLayoutParams) {
PercentLayoutInfo info =
((PercentLayoutParams) params).getPercentLayoutInfo();if(Log.isLoggable(TAG, Log.DEBUG)) {
Log.d(TAG,"using "+ info);
}if(info !=null) {if(paramsinstanceofViewGroup.MarginLayoutParams) {
info.restoreMarginLayoutParams((ViewGroup.MarginLayoutParams) params);
}else{
info.restoreLayoutParams(params);
}
}
}
}
}噗，原来是重新恢复原本的尺寸值，也就是说onMeasure里面的对值进行了改变，测量完成后。在这个地方，将值又恢复成如果布局文件中的值，上面写的都是0。恢复很简单：publicvoidrestoreLayoutParams(ViewGroup.LayoutParams params) {
params.width = mPreservedParams.width;
params.height = mPreservedParams.height;
}你应该没有忘在哪存的把~忘了的话，麻烦Ctrl+F ‘mPreservedParams.width’ 。也就是说，你去打印上面写法，布局文件中view的v.getLayoutParams().width，这个值应该是0。这里感觉略微不爽~这个0没撒用处呀，还不如不重置~~好了，到此就分析完了，其实主要就几个步骤：LayoutParams中属性的获取onMeasure中，改变params.width为百分比计算结果，测量如果测量值过小且设置的w/h是wrap_content，重新测量onLayout中，重置params.w/h为布局文件中编写的值可以看到，有了RelativeLayout、FrameLayout的扩展，竟然没有LinearLayout几个意思。好在，我们的核心代码都由PercentLayoutHelper封装了，自己扩展下LinearLayout也不复杂。三、实现PercentLinearlayout可能有人会说，有了weight呀，但是weight能做到宽、高同时百分比赋值嘛？好了，代码很简单，如下：（一）PercentLinearLayoutpackagecom.juliengenoud.percentsamples;importandroid.content.Context;importandroid.content.res.TypedArray;importandroid.support.percent.PercentLayoutHelper;importandroid.util.AttributeSet;importandroid.view.ViewGroup;importandroid.widget.LinearLayout;/**
* Created by zhy on 15/6/30.
*/publicclassPercentLinearLayoutextendsLinearLayout{privatePercentLayoutHelper mPercentLayoutHelper;publicPercentLinearLayout(Context context, AttributeSet attrs)
{super(context, attrs);
mPercentLayoutHelper =newPercentLayoutHelper(this);
}@OverrideprotectedvoidonMeasure(intwidthMeasureSpec,intheightMeasureSpec)
{
mPercentLayoutHelper.adjustChildren(widthMeasureSpec, heightMeasureSpec);super.onMeasure(widthMeasureSpec, heightMeasureSpec);if(mPercentLayoutHelper.handleMeasuredStateTooSmall())
{super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}
}@OverrideprotectedvoidonLayout(booleanchanged,intl,intt,intr,intb)
{super.onLayout(changed, l, t, r, b);
mPercentLayoutHelper.restoreOriginalParams();
}@OverridepublicLayoutParamsgenerateLayoutParams(AttributeSet attrs)
{returnnewLayoutParams(getContext(), attrs);
}publicstaticclassLayoutParamsextendsLinearLayout.LayoutParamsimplementsPercentLayoutHelper.PercentLayoutParams{privatePercentLayoutHelper.PercentLayoutInfo mPercentLayoutInfo;publicLayoutParams(Context c, AttributeSet attrs)
{super(c, attrs);
mPercentLayoutInfo = PercentLayoutHelper.getPercentLayoutInfo(c, attrs);
}@OverridepublicPercentLayoutHelper.PercentLayoutInfogetPercentLayoutInfo()
{returnmPercentLayoutInfo;
}@OverrideprotectedvoidsetBaseAttributes(TypedArray a,intwidthAttr,intheightAttr)
{
PercentLayoutHelper.fetchWidthAndHeight(this, a, widthAttr, heightAttr);
}publicLayoutParams(intwidth,intheight) {super(width, height);
}publicLayoutParams(ViewGroup.LayoutParams source) {super(source);
}publicLayoutParams(MarginLayoutParams source) {super(source);
}
}
}如果你详细看了上面的源码分析，这个代码是不是没撒解释的了~（二）测试布局我们纵向排列的几个TextView，分别设置宽/高都为百分比，且之间的间隔为5%p。(三)效果图ok，到此，我们使用、源码分析、扩展PercentLinearLayout就结束了。添加PercentLinearLayout后的地址：点击查看~~have a nice day ~~新浪微博微信公众号：hongyangAndroid（欢迎关注，第一时间推送博文信息）