ScreenAdapter

屏幕适配方案 采用百分比适配思路进行屏幕适配

原理说明

采用百分比适配原理,进行屏幕适配 
首先 我们加载布局之后都会走到这个方法

 @Override
 public void setContentView(int resId) {
 ensureSubDecor();
 ViewGroup contentParent = (ViewGroup) mSubDecor.findViewById(android.R.id.content);
 contentParent.removeAllViews();
 LayoutInflater.from(mContext).inflate(resId, contentParent);
 mOriginalWindowCallback.onContentChanged();
 }

继续查看

 public View inflate(@LayoutRes int resource, @Nullable ViewGroup root, boolean attachToRoot) {
 final Resources res = getContext().getResources();
 if (DEBUG) {
 Log.d(TAG, "INFLATING from resource: \"" + res.getResourceName(resource) + "\" ("
 + Integer.toHexString(resource) + ")");
 }
 
 final XmlResourceParser parser = res.getLayout(resource);
 try {
 return inflate(parser, root, attachToRoot);
 } finally {
 parser.close();
 }
 }

这里将布局文件转换成对应的View对象
继续查看解析xml的方法

 XmlResourceParser loadXmlResourceParser(@AnyRes int id, @NonNull String type)
 throws NotFoundException {
 final TypedValue value = obtainTempTypedValue();
 try {
 final ResourcesImpl impl = mResourcesImpl;
 impl.getValue(id, value, true);
 if (value.type == TypedValue.TYPE_STRING) {
 return impl.loadXmlResourceParser(value.string.toString(), id,
 value.assetCookie, type);
 }
 throw new NotFoundException("Resource ID #0x" + Integer.toHexString(id)
 + " type #0x" + Integer.toHexString(value.type) + " is not valid");
 } finally {
 releaseTempTypedValue(value);
 }
 }

最后防线布局中所有的尺寸最后都在这里进行计算转换为px

 public static float applyDimension(int unit, float value,
 DisplayMetrics metrics)
 {
 switch (unit) {
 case COMPLEX_UNIT_PX:
 return value;
 case COMPLEX_UNIT_DIP:
 return value * metrics.density;
 case COMPLEX_UNIT_SP:
 return value * metrics.scaledDensity;
 case COMPLEX_UNIT_PT:
 return value * metrics.xdpi * (1.0f/72);
 case COMPLEX_UNIT_IN:
 return value * metrics.xdpi;
 case COMPLEX_UNIT_MM:
 return value * metrics.xdpi * (1.0f/25.4f);
 }
 return 0;
 }