努力使任何东西都可以在android上的web3j中工作,尝试使用本示例(我已替换了token和addr),我使用的地址确实包含一些rinkeby ETH。在电话上测试,加载此类/活动时应用程序崩溃,代码在oncreate方法中。在清单中打开互联网许可,然后在构建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)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1291)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1107)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at com.test.user.test.balance.onCreate(balance.java:43)
at android.app.Activity.performCreate(Activity.java:5619)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1093)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2512)
错误引用的第43行是我提交的代码中的最后一行代码。当我注释掉该行应用程序不会崩溃时,只会收到一些(我认为是全部)警告。
最佳答案
您的ethGetBalance返回一个空值。我认为您输入了无效的地址。那就是为什么方法
web3j.ethGetBalance失败。尝试使用有效地址。
Web3j web3 = Web3jFactory.build(new HttpService("https://ropsten.infura.io/your-token"));
String strAddress="0x24b********************"; //strAddress is your wallet address
EthGetBalance ethGetBalance=
web3.ethGetBalance(strAddress,DefaultBlockParameterName.LATEST).sendAsync().get();
BigInteger wei = ethGetBalance.getBalance();
ethGetBalance.getBalance()用于获取wei中的以太币余额。
要在您的钱包中获取实际令牌,请使用此Conversion方法。
java.math.BigDecimal tokenValue = Convert.fromWei(String.valueOf(wei), Convert.Unit.ETHER);
String strTokenAmount = String.valueOf(tokenValue);