虽然ConstraintLayout发布已经有几年了，但是笔者还一直未用过。只知道它非常强大，相比以往的布局其不存在view的嵌套，对于解析器及图形渲染就更快，效率自然就高了！“纸上得来终觉浅，绝知此事须(要)躬行”

先引用一篇文章：https://www.jianshu.com/p/17ec9bd6ca8a ，写的可谓意简言赅，文章内容我就不多演示，本文仅展示ConstraintLayout部分功能。

上效果图：

Java代码

package com.lee.lgt;
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.support.constraint.ConstraintLayout.LayoutParams;
import android.view.Window;
import android.widget.TextView;
public class MainActivity extends Activity {
    private LayoutParams params;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        setContentView(R.layout.activity_main);
        final TextView tv = findViewById(R.id.TextView4);
        Handler handler = new Handler() {
            @Override
            public void handleMessage(Message msg) {
                super.handleMessage(msg);
                params.circleAngle += 5f;
                tv.setLayoutParams(params);
                removeMessages(msg.what);
                sendEmptyMessageDelayed((int) params.circleAngle % 360, 10);
            }
        };
        if (tv.getLayoutParams() instanceof LayoutParams) {
            params = (LayoutParams) tv.getLayoutParams();
            handler.sendEmptyMessageDelayed((int) params.circleAngle, 1000);
        }
    }
}

xml代码

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">
    <TextView
        android:id="@+id/TextView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:background="@color/colorAccent"
        android:text="111"
        android:textColor="@android:color/white"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintHorizontal_weight="1"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toLeftOf="@id/TextView2"
        app:layout_constraintTop_toTopOf="parent" />
    <TextView
        android:id="@+id/TextView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:background="@color/colorPrimary"
        android:text="222"
        android:textColor="@android:color/white"
        app:layout_constraintHorizontal_weight="3"
        app:layout_constraintLeft_toRightOf="@id/TextView1"
        app:layout_constraintRight_toLeftOf="@id/TextView3"
        app:layout_constraintTop_toTopOf="@id/TextView1" />
    <TextView
        android:id="@+id/TextView3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:background="@color/colorPrimaryDark"
        android:text="333"
        android:textColor="@android:color/white"
        app:layout_constraintHorizontal_weight="5"
        app:layout_constraintLeft_toRightOf="@id/TextView2"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="@id/TextView1" />
    <TextView
        android:id="@+id/TextView4"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:background="@color/colorPrimaryDark"
        android:text="444"
        android:textColor="@android:color/white"
        app:layout_constraintCircle="@id/TextView1"
        app:layout_constraintCircleAngle="150"
        app:layout_constraintCircleRadius="50dp"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
    <TextView
        android:id="@+id/TextView5"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginTop="30dp"
        android:background="@color/colorAccent"
        android:text="555"
        android:textColor="@android:color/white"
        app:layout_constraintHorizontal_weight="2"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toLeftOf="@id/TextView6"
        app:layout_constraintTop_toBottomOf="@id/TextView4" />
    <TextView
        android:id="@+id/TextView6"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:background="@color/colorPrimary"
        android:text="666"
        android:textColor="@android:color/white"
        app:layout_constraintHorizontal_weight="3"
        app:layout_constraintLeft_toRightOf="@id/TextView5"
        app:layout_constraintRight_toLeftOf="@id/TextView7"
        app:layout_constraintTop_toTopOf="@id/TextView5" />
    <TextView
        android:id="@+id/TextView7"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:background="@color/colorPrimaryDark"
        android:text="777"
        android:textColor="@android:color/white"
        app:layout_constraintHorizontal_weight="5"
        app:layout_constraintLeft_toRightOf="@id/TextView2"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="@id/TextView5" />
    <TextView
        android:id="@+id/TextView8"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="30dp"
        android:background="@color/colorAccent"
        android:text="888"
        android:textColor="@android:color/white"
        app:layout_constraintHorizontal_bias="0.2"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toBottomOf="@id/TextView5" />
    <TextView
        android:id="@+id/TextView9"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="30dp"
        android:background="@color/colorPrimary"
        android:text="999"
        android:textColor="@android:color/white"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toBottomOf="@id/TextView5" />
    <TextView
        android:id="@+id/TextViewA"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="30dp"
        android:background="@color/colorPrimaryDark"
        android:text="999"
        android:textColor="@android:color/white"
        app:layout_constraintHorizontal_bias="0.9"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toBottomOf="@id/TextView5" />
</android.support.constraint.ConstraintLayout>

总共就2层搞定所有需求，是不是感觉强大呢？

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