jdk 8 lambda表達式 及在Android Studio的使用示例

以前覺得java讓人覺得有趣的一個特點是支持：匿名內部類，而最近發現jdk8已支持lambda並有更簡便的方式，來實現匿名內部類. 這會讓程序員更舒服，更喜歡java. 多年前覺得java語法和C#語法差得有點遠，沒有C#那么寫來方便，現在覺得jdk8也很不錯了。做技術還是要向前看。

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 改變");
    }
});

新的實現方式：

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 改變:" + new Date().toString());
});

 

參考：

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'
}