jdk 8 lambda表达式 及在Android Studio的使用示例

Posted 2020-08-04 庚武讲堂

以前觉得java让人觉得有趣的一个特点是支持：匿名内部类，而最近发现jdk8已支持lambda并有更简便的方式，来实现匿名内部类. 这会让程序员更舒服，更喜欢java. 多年前觉得java语法和C#语法差得有点远，没有C#那么写来方便，现在觉得jdk8也很不错了。做技术还是要向前看。

final TextView txtView2 = (TextView)this.findViewById(R.id.txtView2);
Button btnChangeView = (Button)findViewById(R.id.btnChangeText);

btnChangeView.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
        txtView2.setText("Text 改变");
    }
});

新的实现方式：

final TextView txtView2 = (TextView)this.findViewById(R.id.txtView2);
Button btnChangeView = (Button)findViewById(R.id.btnChangeText);

//btnChangeView.setOnClickListener(e -> Log.i("MyTag", "Button Clicked.") );
assert btnChangeView != null;
btnChangeView.setOnClickListener((view) -> {
    Log.i(TAG, "btnChangeView Clicked:" + view.getId());
    txtView2.setText("Text 改变:" + new Date().toString());
});

 

参考：

http://stackoverflow.com/questions/37004069/errorjack-is-required-to-support-java-8-language-features

http://www.jianshu.com/p/5fc2b3362702

需要更改配置: build.gradle

defaultConfig {
  ...
    jackOptions {
      enabled true
    }
  }

  compileOptions {
    sourceCompatibility JavaVersion.VERSION_1_8
    targetCompatibility JavaVersion.VERSION_1_8
  }

apply plugin: ‘com.android.application‘

android {
    compileSdkVersion 23
    buildToolsVersion "24.0.2"

    defaultConfig {
        applicationId "com.firstapp.test.firstapp"
        minSdkVersion 16
        targetSdkVersion 23
        versionCode 1
        versionName "1.0"
        jackOptions {
            enabled true
        }
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile(‘proguard-android.txt‘), ‘proguard-rules.pro‘
        }
    }
    compileOptions {
        sourceCompatibility 1.8
        targetCompatibility 1.8
    }
}

dependencies {
    compile fileTree(include: [‘*.jar‘], dir: ‘libs‘)
    testCompile ‘junit:junit:4.12‘
    compile ‘com.android.support:appcompat-v7:23.4.0‘
}