小编web*_*per的帖子

努力让任何东西在android上的web3j中工作，尝试这个例子（我已经替换了token和addr），我使用的地址确实有一些rinkeby ETH。在手机上测试，当我加载此类/活动时，应用程序崩溃，代码位于 oncreate 方法中。在清单中打开互联网权限，并在构建 gradle 中编译 android web3j。

 Web3j web3 = Web3jFactory.build(new 
 HttpService("https://rinkeby.infura.io/token"));

    EthGetBalance ethGetBalance = null;
    try {
        ethGetBalance = web3
                .ethGetBalance("addr",DefaultBlockParameterName.LATEST)
                .sendAsync()
                .get();
    } catch (InterruptedException e) {
        e.printStackTrace();
    } catch (ExecutionException e) {
        e.printStackTrace();
    }

    BigInteger wei = ethGetBalance.getBalance();

错误

06-30 02:15:47.115 18904-18904/? E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.test.user.test, PID: 18904
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.test.user.test/com.test.user.test.balance}: java.lang.NullPointerException
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2548)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2607)
    at android.app.ActivityThread.access$900(ActivityThread.java:174)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1325)
    at android.os.Handler.dispatchMessage(Handler.java:102)
    at android.os.Looper.loop(Looper.java:146)
    at android.app.ActivityThread.main(ActivityThread.java:5756)
    at java.lang.reflect.Method.invokeNative(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:515) …