我在内部asynctask类中有一个静态Integer currentheartbeat它显示了值，但是在asynctask类之外它看起来是null，我似乎无法达到它。它的原因是什么？
我的班级：
package com.berkkarabacak.mspproje;
import android.app.Activity;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.widget.TextView;
import com.microsoft.azure.storage.CloudStorageAccount;
import com.microsoft.azure.storage.blob.CloudBlob;
import com.microsoft.azure.storage.blob.CloudBlobClient;
import com.microsoft.azure.storage.blob.CloudBlobContainer;
import com.microsoft.azure.storage.blob.CloudBlockBlob;
import com.microsoft.azure.storage.blob.ListBlobItem;
import java.io.File;
import java.io.FileInputStream;
public class Checkactivity extends ActionBarActivity {
String tcnumara;
static Integer currentheartbeat;
static String currentheartbeatstring;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.checkheartbeat);
Bundle extras = getIntent().getExtras();
if (extras != null) {
tcnumara = extras.getString("tcnumber");
}
TextView t = (TextView) findViewById(R.id.tcnumaraset);
t.setText(tcnumara);
new Azure().execute();
System.out.print(currentheartbeat);
System.out.print(currentheartbeat);
System.out.print(currentheartbeat);
System.out.print(currentheartbeat);
currentheartbeatstring=Integer.toString(currentheartbeat);
TextView t2=(TextView)findViewById(R.id.currentheartbeat);
t2.setText(currentheartbeatstring);
}
public class Azure extends AsyncTask<Void, Void, Void> {
public static final String ConnectionString =
"DefaultEndpointsProtocol=http;"
+ "AccountName=mspproje;"
+ "AccountKey=bpBHfSA4uVJVJjxaQcOCKTH7Hib/NAJslvOvnl6q65x652mUahzu6JXKPxAhyP8/w/WKp0htVS5/EVhjaGTkaA==";
@Override
protected Void doInBackground(Void... voids) {
try
{
// Retrieve storage account from connection-string.
CloudStorageAccount storageAccount = CloudStorageAccount.parse(ConnectionString);
// Create the blob client.
CloudBlobClient blobClient = storageAccount.createCloudBlobClient();
// Retrieve reference to a previously created container.
CloudBlobContainer container = blobClient.getContainerReference("mspproje");
// Define the path to a local file.
final String filePath = "C:\\Users\\Berk\\Desktop\\audi.jpg";
// Create or overwrite the "myimage.jpg" blob with contents from a local file.
CloudBlockBlob blob = container.getBlockBlobReference(MainActivity.tcnumara+".csv");
String lastelementdeleted=blob.downloadText().substring(0, blob.downloadText().length() - 1);
currentheartbeat=Integer.parseInt(lastelementdeleted.substring(lastelementdeleted.lastIndexOf(";")+2));
System.out.println(currentheartbeat+"in inner async try");
}
catch (Exception e)
{
// Output the stack trace.
e.printStackTrace();
}
return null;
}
}
}
在logcat中，您可以看到它在内部异步类中显示52但在主外部类中它看起来为空
04-16 00:35:03.244 30866-30866/com.berkkarabacak.mspproje E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.berkkarabacak.mspproje, PID: 30866
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.berkkarabacak.mspproje/com.berkkarabacak.mspproje.Checkactivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'int java.lang.Integer.intValue()' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2693)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2758)
at android.app.ActivityThread.access$900(ActivityThread.java:177)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1448)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:5942)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1389)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1184)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'int java.lang.Integer.intValue()' on a null object reference
at com.berkkarabacak.mspproje.Checkactivity.onCreate(Checkactivity.java:41)
at android.app.Activity.performCreate(Activity.java:6283)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1119)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2646)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2758)
at android.app.ActivityThread.access$900(ActivityThread.java:177)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1448)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:5942)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1389)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1184)
04-16 00:35:03.324 30866-31340/com.berkkarabacak.mspproje I/System.out﹕ nullnullnullnull(HTTPLog)-Static: isSBSettingEnabled false
04-16 00:35:03.324 30866-31340/com.berkkarabacak.mspproje I/System.out﹕ (HTTPLog)-Static: isShipBuild true
04-16 00:35:03.324 30866-31340/com.berkkarabacak.mspproje I/System.out﹕ (HTTPLog)-Thread-17315-974616881: SmartBonding Enabling is false, SHIP_BUILD is true, log to file is false, DBG is false
04-16 00:35:03.324 30866-31340/com.berkkarabacak.mspproje I/System.out﹕ (HTTPLog)-Static: isSBSettingEnabled false
04-16 00:35:03.504 30866-31340/com.berkkarabacak.mspproje I/System.out﹕ KnoxVpnUidStorageknoxVpnSupported API value returned is false
04-16 00:35:03.699 30866-31340/com.berkkarabacak.mspproje I/System.out﹕ (HTTPLog)-Static: isSBSettingEnabled false
04-16 00:35:03.774 30866-31340/com.berkkarabacak.mspproje I/System.out﹕ 52in inner async try
答案 0 :(得分：1)
currentheartbeat以null值开头。
您正在尝试在AsyncTask有时间从Azure获取值之前打印它。
基本上你的Azure AsyncTask在后台运行 - 执行行只是在后台开始下载并立即执行下一行，此时变量为空。