android demo，ConstraintLayout 约束布局

android demo，ConstraintLayout （约束布局），该demo详细的介绍了layout_constraint布局的所有属性。

/* AUTO-GENERATED FILE.  DO NOT MODIFY.
 *
 * This class was automatically generated by the
 * gradle plugin from the resource data it found. It
 * should not be modified by hand.
 */
package android.arch.lifecycle;

public final class R {
    private R（） {}

}

 属性            大小     日期    时间   名称
----------- ---------  ---------- -----  ----
     目录           0  2019-05-28 17:54  android-constraintlayout\
     文件        1409  2019-05-23 05:01  android-constraintlayout\versions.gradle
     目录           0  2019-05-28 17:55  __MACOSX\
     目录           0  2019-05-28 17:55  __MACOSX\android-constraintlayout\
     文件         212  2019-05-23 05:01  __MACOSX\android-constraintlayout\._versions.gradle
     目录           0  2019-05-28 17:55  android-constraintlayout\app\
     文件       13959  2019-05-28 17:55  android-constraintlayout\app\app.iml
     文件         751  2019-05-23 05:01  android-constraintlayout\app\proguard-rules.pro
     目录           0  2019-05-28 17:55  __MACOSX\android-constraintlayout\app\
     文件         212  2019-05-23 05:01  __MACOSX\android-constraintlayout\app\._proguard-rules.pro
     文件           7  2019-05-23 05:01  android-constraintlayout\app\.gitignore
     文件         212  2019-05-23 05:01  __MACOSX\android-constraintlayout\app\._.gitignore
     文件        1121  2019-05-28 17:54  android-constraintlayout\app\build.gradle
     目录           0  2019-05-28 17:55  android-constraintlayout\app\build\
     目录           0  2019-05-28 17:55  android-constraintlayout\app\build\generated\
     目录           0  2019-05-28 17:54  android-constraintlayout\app\build\generated\res\
     目录           0  2019-05-28 17:54  android-constraintlayout\app\build\generated\res\pngs\
     目录           0  2019-05-28 17:54  android-constraintlayout\app\build\generated\res\pngs\debug\
     目录           0  2019-05-28 17:54  android-constraintlayout\app\build\generated\res\pngs\debug\drawable-xhdpi\
     文件        1320  2019-05-28 17:54  android-constraintlayout\app\build\generated\res\pngs\debug\drawable-xhdpi\ic_launcher_background.png
     目录           0  2019-05-28 17:54  android-constraintlayout\app\build\generated\res\pngs\debug\drawable-xxhdpi\
     文件        3254  2019-05-28 17:54  android-constraintlayout\app\build\generated\res\pngs\debug\drawable-xxhdpi\ic_launcher_background.png
     目录           0  2019-05-28 17:54  android-constraintlayout\app\build\generated\res\pngs\debug\drawable-hdpi\
     文件         730  2019-05-28 17:54  android-constraintlayout\app\build\generated\res\pngs\debug\drawable-hdpi\ic_launcher_background.png
     目录           0  2019-05-28 17:54  android-constraintlayout\app\build\generated\res\pngs\debug\drawable-ldpi\
     文件         331  2019-05-28 17:54  android-constraintlayout\app\build\generated\res\pngs\debug\drawable-ldpi\ic_launcher_background.png
     目录           0  2019-05-28 17:54  android-constraintlayout\app\build\generated\res\pngs\debug\drawable-anydpi-v21\
     文件        5606  2019-05-28 17:54  android-constraintlayout\app\build\generated\res\pngs\debug\drawable-anydpi-v21\ic_launcher_background.xml
     目录           0  2019-05-28 17:54  android-constraintlayout\app\build\generated\res\pngs\debug\drawable-mdpi\
     文件         407  2019-05-28 17:54  android-constraintlayout\app\build\generated\res\pngs\debug\drawable-mdpi\ic_launcher_background.png
     目录           0  2019-05-28 17:54  android-constraintlayout\app\build\generated\res\pngs\debug\drawable-xxxhdpi\
............此处省略1304个文件信息