Android Studio update (1.5 to 2.2.3) breaks project

问题

So i've updated my Android Studio from Version 1.5 to 2.2.3 and this completely broke my project. I'm pretty new at programming and my app worked just fine before, but now, every single android library import is marked red.

import android.animation.ArgbEvaluator;
import android.animation.ValueAnimator;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.content.pm.ActivityInfo;
import android.graphics.Color;
import android.media.MediaPlayer;
import android.os.CountDownTimer;

for example, none of these are recognized any more. I've updated everything Android Studio wanted me to, but tbh i don't know how to fix this.

My gradle file looks like the following:

apply plugin: 'com.android.application'

android {
    compileSdkVersion 23
    buildToolsVersion "23.0.3"

    defaultConfig {
        applicationId "com.example.privatpc.quiztest"
        minSdkVersion 16
        targetSdkVersion 23
        versionCode 1
        versionName "1.0"
        multiDexEnabled true
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    testCompile 'junit:junit:4.12'
    compile 'com.android.support:appcompat-v7:23.1.1'

}

build.gradle

// Top-level build file where you can add configuration options common to all sub-projects/modules.


buildscript {
    repositories {
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:2.2.3'
        classpath 'com.google.gms:google-services:3.0.0'

        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
    }
}

allprojects {
    repositories {
        jcenter()
    }
}

task clean(type: Delete) {
    delete rootProject.buildDir
}

Update: Doing File-> "Invalidate Caches/Restart" seemed to work. Now the next Problem is the following:

Once i try running the project the app opens and immediately crashes. I get the following log:

java.lang.IllegalStateException: You need to use a Theme.AppCompat theme (or descendant) with this activity.

回答1:

Try doing this in build.gradle

buildscript {repositories {jcenter()}dependencies {classpath 'com.android.tools.build:gradle:2.2.3'}}

回答2:

If you are trying on devices below Android 7, generate APK by using V1 signature instead of V2. All apps will crash if you select V2 Signature because it is targeting for Android 7.

signature

来源：https://stackoverflow.com/questions/42299065/android-studio-update-1-5-to-2-2-3-breaks-project

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