android - FloatingActionButton 类无法实例化

Question

在了解了 Material Design 中的新方法后，我尝试在应用中实现一个 float 操作按钮。但是，我在预览(预览 Android 版本 21)中遇到此错误:

The following classes could not be instantiated:
- android.support.design.widget.FloatingActionButton
(First paragraph of error)
java.lang.NullPointerException
at android.support.v4.graphics.drawable.DrawableCompatLollipop.setTintList(DrawableCompatLollipop.java:56)
at android.support.v4.graphics.drawable.DrawableCompat$LollipopDrawableImpl.setTintList(DrawableCompat.java:145)
at android.support.v4.graphics.drawable.DrawableCompat.setTintList(DrawableCompat.java:270)
etc...

有人知道吗？这是我的 build.gradle:

android {
compileSdkVersion 22
buildToolsVersion "22.0.1"
classpath 'com.android.tools.build:gradle:1.2.3'


defaultConfig {
    applicationId "owensetiawan.tutorials.fab"
    minSdkVersion 15
    targetSdkVersion 22
    versionCode 1
    versionName "1.0"
}
buildTypes {
    release {
        minifyEnabled false
        proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
    }
}
}

dependencies {
compile fileTree(dir: 'libs', include: ['*.jar'])
compile 'com.android.support:appcompat-v7:22.2.0'
compile 'com.android.support:design:22.2.0'
}

如果有人能帮助我阐明我的问题，那就太好了。

Answer 1

嘿，我在实例化设计库时遇到了同样的问题，并通过这个解决了

第 1 步 > fab 代码

    <android.support.design.widget.FloatingActionButton
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_gravity="bottom"
      android:clickable="true"
      android:src="@drawable/search"
      app:backgroundTint="@color/color_fav"
      app:borderWidth="0dp"
      android:layout_alignParentBottom="true"
      android:layout_alignParentEnd="true"
      />

第二步>依赖

    compile 'com.android.support:appcompat-v7:22.2.1'
    compile 'com.android.support:recyclerview-v7:22.2.1'
    compile 'com.android.support:design:22.2.1'
    compile "com.android.support:support-v4:22.2.1"

步骤3>解决上述问题的主要步骤

简单的:- 转到您的 xml 并单击预览，然后在预览栏中选择 AP1 21