安卓開發學習------4.約束佈局(ConstraintLayout)實現一個計算器

約束佈局是在安卓9之後提出的一種佈局方式,相比較之前的佈局方式,優點是:
在這裏插入圖片描述
示例:

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.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=".YueshuActivity">

    <TextView
        android:layout_width="match_parent"
        android:layout_height="150dp"
        android:textSize="100dp"
        android:textColor="#3CB371"
        android:gravity="right"
        android:text="0"
        android:id="@+id/tv1"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        />
    <Button

        app:layout_constraintHorizontal_weight="1"
        app:layout_constraintRight_toLeftOf="@id/btn_back"
        android:textColor="#ff0000"
        app:layout_constraintTop_toBottomOf="@id/tv1"
        app:layout_constraintLeft_toLeftOf="parent"
        android:id="@+id/btn_c"
        android:layout_width="0dp"
        android:layout_height="100dp"
        android:text="C"
        android:textSize="35dp"
        />
    <Button
        android:layout_width="0dp"
        android:layout_height="100dp"
        app:layout_constraintHorizontal_weight="1"
        android:text="Back"
        android:textSize="20dp"
        app:layout_constraintTop_toBottomOf="@id/tv1"
        app:layout_constraintLeft_toRightOf="@id/btn_c"
        app:layout_constraintRight_toLeftOf="@id/btn_per"
        android:layout_below="@id/tv1"
        android:id="@+id/btn_back"
        />
    <Button
        android:layout_width="0dp"
        android:layout_height="100dp"
        app:layout_constraintHorizontal_weight="1"
        android:text="%"
        android:textSize="30dp"
        app:layout_constraintTop_toBottomOf="@id/tv1"
        app:layout_constraintLeft_toRightOf="@id/btn_back"
        app:layout_constraintRight_toLeftOf="@id/btn_muv"
        android:id="@+id/btn_per"
        />
    <Button
        android:layout_width="0dp"
        android:layout_height="100dp"
        android:text="*"
        android:textSize="30dp"
        app:layout_constraintHorizontal_weight="1"
        app:layout_constraintTop_toBottomOf="@id/tv1"
        app:layout_constraintLeft_toRightOf="@id/btn_per"
        app:layout_constraintRight_toRightOf="parent"
        android:id="@+id/btn_muv"
        />
    <Button
        android:layout_width="100dp"
        android:layout_height="100dp"

        android:text="9"
        android:textSize="35dp"

        app:layout_constraintTop_toBottomOf="@id/btn_c"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toLeftOf="@id/btn_8"
        android:id="@+id/btn_9"
        />
    <Button
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:text="8"
        android:textSize="35dp"

        app:layout_constraintTop_toBottomOf="@id/btn_c"
        app:layout_constraintLeft_toRightOf="@id/btn_9"
        app:layout_constraintRight_toLeftOf="@id/btn_7"
        android:id="@+id/btn_8"
        />
    <Button
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:text="7"
        android:textSize="35dp"

        app:layout_constraintTop_toBottomOf="@id/btn_c"
        app:layout_constraintLeft_toRightOf="@id/btn_8"
        app:layout_constraintRight_toLeftOf="@id/btn_dev"
        android:id="@+id/btn_7"
        />
    <Button
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:text="/"
        android:textSize="35dp"

        app:layout_constraintTop_toBottomOf="@id/btn_c"
        app:layout_constraintLeft_toRightOf="@id/btn_7"
        app:layout_constraintRight_toRightOf="parent"
        android:id="@+id/btn_dev"
        />
    <Button
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:text="6"
        android:textSize="35dp"
        app:layout_constraintTop_toBottomOf="@id/btn_9"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toLeftOf="@id/btn_5"
        android:id="@+id/btn_6"
        />
    <Button
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:text="5"
        android:textSize="35dp"
        app:layout_constraintTop_toBottomOf="@id/btn_9"
        app:layout_constraintLeft_toRightOf="@id/btn_6"
        app:layout_constraintRight_toLeftOf="@id/btn_4"
        android:id="@+id/btn_5"
        />
    <Button
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:text="4"
        android:textSize="35dp"
        app:layout_constraintTop_toBottomOf="@id/btn_9"
        app:layout_constraintLeft_toRightOf="@id/btn_5"
        app:layout_constraintRight_toLeftOf="@id/btn_muv"
        android:id="@+id/btn_4"
        />
    <Button
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:text="-"
        android:textSize="35dp"
        app:layout_constraintTop_toBottomOf="@id/btn_9"
        app:layout_constraintLeft_toRightOf="@id/btn_4"
        app:layout_constraintRight_toRightOf="parent"
        android:id="@+id/btn_sub"
        />
    <Button
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:text="3"
        android:textSize="35dp"
        app:layout_constraintTop_toBottomOf="@id/btn_6"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toLeftOf="@id/btn_2"
        android:id="@+id/btn_3"
        />
    <Button
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:text="2"
        android:textSize="35dp"
        app:layout_constraintTop_toBottomOf="@id/btn_6"
        app:layout_constraintLeft_toRightOf="@id/btn_3"
        app:layout_constraintRight_toLeftOf="@id/btn_1"
        android:id="@+id/btn_2"
        />
    <Button
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:text="1"
        android:textSize="35dp"
        app:layout_constraintTop_toBottomOf="@id/btn_6"
        app:layout_constraintLeft_toRightOf="@id/btn_2"
        app:layout_constraintRight_toLeftOf="@id/btn_add"
        android:id="@+id/btn_1"
        />
    <Button
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:text="+"
        android:textSize="35dp"
        app:layout_constraintTop_toBottomOf="@id/btn_6"
        app:layout_constraintLeft_toRightOf="@id/btn_1"
        app:layout_constraintRight_toRightOf="parent"
        android:id="@+id/btn_add"
        />
    <Button
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:text="+/-"
        android:textSize="35dp"
        app:layout_constraintTop_toBottomOf="@id/btn_3"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toLeftOf="@id/btn_0"
        android:id="@+id/btn_zf"
        />
    <Button
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:text="0"
        android:textSize="35dp"
        app:layout_constraintTop_toBottomOf="@id/btn_3"
        app:layout_constraintLeft_toRightOf="@id/btn_zf"
        app:layout_constraintRight_toLeftOf="@id/btn_poi"
        android:id="@+id/btn_0"
        />
    <Button
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:text="."
        android:textSize="35dp"
        app:layout_constraintTop_toBottomOf="@id/btn_3"
        app:layout_constraintLeft_toRightOf="@id/btn_0"
        app:layout_constraintRight_toLeftOf="@id/btn_result"
        android:id="@+id/btn_poi"
        />
    <Button
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:text="="
        android:textSize="35dp"
        app:layout_constraintTop_toBottomOf="@id/btn_3"
        app:layout_constraintLeft_toRightOf="@id/btn_poi"
        app:layout_constraintRight_toRightOf="parent"
        android:id="@+id/btn_result"
        />



</androidx.constraintlayout.widget.ConstraintLayout>

結果:
在這裏插入圖片描述

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