空指针异常：....对空对象引用'android.bluetooth.le.ScanRecord android.bluetooth.le.ScanResult.getScanRecord()'的

Question

我在这行代码中使用函数getScanRecord:

if (!(this.mScanResult.getScanRecord().getServiceData() == null || this.mScanResult.getScanRecord().getServiceData().size() == 0)) {
advertisementData = advertisementData + "Service Data: " + this.mScanResult.getScanRecord().getServiceData().toString().replace('{', ' ').replace('}', ' ') + "n";
}

它在Android Studio中给了我这个错误:

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.catu.catucomm/com.catu.catucomm.Second}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.bluetooth.le.ScanRecord android.bluetooth.le.ScanResult.getScanRecord()' on a null object reference

Answer 1

我已经通过这样初始化变量解决了这个问题:

private ScanResult mScanResult;
public Second(ScanResult mScanResult) 
{
this.mScanResult = mScanResult;
}

但是现在我有了新的问题:

. lang。InstantiationException: java.lang.Class没有零参数构造函数

Answer 2

根据您的错误消息，我怀疑您的'mScanResult'变量为空。检查你的'mScanResult'是否为空

试试这个。

/*Listener sur le btn Pair*/
mPairBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent(MainActivity.this,Second.class);
intent.putExtra(EXTRAS_SCAN_RESULT, -YOU NEED TO PUT YOUR SCAN RESULT HERE- );
startActivity(intent);
finish();
}
});

您需要使用putExtra()函数将扫描结果对象传递给第二个活动。