《第一行代码》学习百分比布局所遇到的问题

学习百分比布局时遇到的问题

在《第一行代码》中学习百分比布局时需要在bulid.gradle中dependencies闭包中添加百分比布局库的依赖，书上的代码如下：

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    compile 'com.android.support:appcompat-v7:24.2.1'
    compile 'com.android.support:percent:24.2.1'
    testCompile 'junit:junit:4.12'
}

添加书上代码后：

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'androidx.appcompat:appcompat:1.0.2'
    implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
    compile 'com.android.support:appcompat-v7:24.2.1'
    compile 'com.android.support:percent:24.2.1'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'androidx.test:runner:1.2.0'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0'
}

Sync gradle后报如下错误：

WARNING: Configuration 'compile' is obsolete and has been replaced with 'implementation' and 'api'.
It will be removed at the end of 2018. For more information see: http://d.android.com/r/tools/update-dependency-configurations.html

参考错误后发现新版本不使用’compile’来添加依赖，应修改为 ‘implementation’ 或 ‘api’，我修改为implementation：

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'androidx.appcompat:appcompat:1.0.2'
    implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
    implementation 'com.android.support:appcompat-v7:24.2.1'
    implementation 'com.android.support:percent:24.2.1'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'androidx.test:runner:1.2.0'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0'
}

修改后发现仍然报错：

Version 28 (intended for Android Pie and below) is the last version of the legacy support library, so we recommend that you migrate to AndroidX libraries when using Android Q and moving forward. The IDE can help with this: Refactor > Migrate to AndroidX... less... (Ctrl+F1) 
Inspection info:There are some combinations of libraries, or tools and libraries, that are incompatible, or can lead to bugs. One such incompatibility is compiling with a version of the Android support libraries that is not the latest version (or in particular, a version lower than your targetSdkVersion).  Issue id: GradleCompatible

通过观察后发现原来添加的库版本太低，参考build.gradle中安卓compileSdkVersion为29.0.0，因此修改库版本为29.0.0：

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'androidx.appcompat:appcompat:1.0.2'
    implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
    implementation 'com.android.support:appcompat-v7:29.0.0'
    implementation 'com.android.support:percent:29.0.0'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'androidx.test:runner:1.2.0'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0'
}

Sync gradle后无报错，添加百分比布局库成功。
然后在布局时按照书上的代码：

<android.support.percent.PercentFrameLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
android.support.percent.PercentFrameLayout>

发现新建布局时布局无法显示，随后发现原来android.support已经迁移至androidx，可在gradle.properties中看到相关代码：

android.useAndroidX=true
android.enableJetifier=true

第一行代码表示当前项目是否启用androidx，第二行代码表示是否将依赖包迁移至androidx。
因此新建布局时需要以androidx为路径的开头，修改代码如下：

<androidx.percentlayout.widget.PercentFrameLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
androidx.percentlayout.widget.PercentFrameLayout>

运行后无发现问题，以上就是我在《第一行代码》中学习百分比布局时所遇到的问题和解决方法。