有时根据项目需要，AndroidManifest.xml中的meta-data的值分测试和正式

为了能自动地更换meta-data值，就需要用到manifestPlaceholders

语法：manifestPlaceholders = [FieldName: FieldValue]

示例如下

build.gradle (Module: app)

apply plugin: 'com.android.application'android {    compileSdkVersion 28    defaultConfig {        applicationId "com.bu_ish.debug_release_test"        minSdkVersion 19        targetSdkVersion 28        versionCode 1        versionName "1.0"        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"    }    buildTypes {        release {            minifyEnabled false            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'            buildConfigField "String", "TextToShow", "\"当前处于发布模式\""            manifestPlaceholders = [ManifestField: "发布模式下的清单字段"]        }        debug {            buildConfigField "String", "TextToShow", "\"当前处于调试模式\""            manifestPlaceholders = [ManifestField: "调试模式下的清单字段"]        }    }}dependencies {    implementation fileTree(dir: 'libs', include: ['*.jar'])    implementation 'com.android.support:appcompat-v7:28.0.0'    testImplementation 'junit:junit:4.12'    androidTestImplementation 'com.android.support.test:runner:1.0.2'    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'}

AndroidManifest.xml

上例中，名为ManifestField的meta-data的值为"发布模式下的清单字段"（Release模式下）或"调试模式下的清单字段"（Debug模式下）

获取该meta-data的示例如下

try {                    String manifestField = getPackageManager().getApplicationInfo(getPackageName(), PackageManager.GET_META_DATA).metaData.getString("ManifestField");                    new AlertDialog.Builder(MainActivity.this).setMessage(manifestField).show();                } catch (PackageManager.NameNotFoundException ex) {                    Log.e(TAG, null, ex);                }