java - 在Android中将数据从一个Java文件传递到另一个

Question

我是 Android 开发的新手。我的项目中有两个 Java 文件。一个文件包含我的主要 Activity ，因此我想将数据从一个 Java 文件传输到另一个包含主要 Activity 的文件。

cordovaExample.java:

package org.apache.cordova.example;

import android.content.Context;
import android.content.Intent;
import android.telephony.*;
import android.app.Activity;
import android.os.Bundle;
import android.widget.Toast;

import org.apache.cordova.*;
public class cordovaExample extends DroidGap
{
@Override
 public void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    super.loadUrl("file:///android_asset/www/index.html");

    Bundle extras = getIntent().getExtras();
    String phno = extras.getString("novel.PhoneNumber");
   Toast.makeText(getApplicationContext(),phno,Toast.LENGTH_LONG).show();



}
}

小说.java

package org.apache.cordova.example;

import android.content.Context;
import android.content.Intent;
import android.telephony.*;
import android.app.Activity;
import android.os.Bundle;
import android.widget.Toast;

public class novel extends Activity
{ 
public String PhoneNumber;
Context mcontext;
public String getNumber()
{



 TelephonyManager tMgr=(TelephonyManager)mcontext.getSystemService(Context.TELEPHONY_SERVICE); 

         Intent intent = new Intent(this, cordovaExample.class);
            intent.putExtra("novel.PhoneNumber", PhoneNumber);
                startActivity(intent);
               return PhoneNumber = tMgr.getLine1Number();
        }

}

所以我想将 "PhoneNumber" 从 novel.java 转移到 cordovaExample.java 但在 novel.java，运行应用程序后，我在模拟器中收到“不幸的是应用程序已停止”。

这是日志

08-12 15:49:37.657: E/AndroidRuntime(779): FATAL EXCEPTION: main
08-12 15:49:37.657: E/AndroidRuntime(779): java.lang.RuntimeException: Unable to start activity  ComponentInfo{org.apache.cordova.example/org.apache.cordova.example.cordovaExample}: java.lang.NullPointerException
08-12 15:49:37.657: E/AndroidRuntime(779):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1956)
08-12 15:49:37.657: E/AndroidRuntime(779):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)
08-12 15:49:37.657: E/AndroidRuntime(779):  at android.app.ActivityThread.access$600(ActivityThread.java:123)
08-12 15:49:37.657: E/AndroidRuntime(779):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
08-12 15:49:37.657: E/AndroidRuntime(779):  at android.os.Handler.dispatchMessage(Handler.java:99)
08-12 15:49:37.657: E/AndroidRuntime(779):  at android.os.Looper.loop(Looper.java:137)
08-12 15:49:37.657: E/AndroidRuntime(779):  at android.app.ActivityThread.main(ActivityThread.java:4424)
08-12 15:49:37.657: E/AndroidRuntime(779):  at java.lang.reflect.Method.invokeNative(Native Method)
08-12 15:49:37.657: E/AndroidRuntime(779):  at java.lang.reflect.Method.invoke(Method.java:511)
08-12 15:49:37.657: E/AndroidRuntime(779):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
08-12 15:49:37.657: E/AndroidRuntime(779):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
08-12 15:49:37.657: E/AndroidRuntime(779):  at dalvik.system.NativeStart.main(Native Method)
08-12 15:49:37.657: E/AndroidRuntime(779): Caused by: java.lang.NullPointerException
08-12 15:49:37.657: E/AndroidRuntime(779):  at org.apache.cordova.example.cordovaExample.onCreate(cordovaExample.java:20)
08-12 15:49:37.657: E/AndroidRuntime(779):  at android.app.Activity.performCreate(Activity.java:4465)
08-12 15:49:37.657: E/AndroidRuntime(779):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
08-12 15:49:37.657: E/AndroidRuntime(779):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1920)
08-12 15:49:37.657: E/AndroidRuntime(779):  ... 11 more

此外，如果我尝试简单的程序，我会得到相同的结果:

cordovaExample.java

package org.apache.cordova.example;

import android.content.Context;
import android.content.Intent;
import android.telephony.*;
import android.app.Activity;
import android.os.Bundle;
import android.widget.Toast;

import org.apache.cordova.*;
public class cordovaExample extends DroidGap
{
@Override
 public void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    super.loadUrl("file:///android_asset/www/index.html");

   novel c=new novel()
   int a=c.getNumber();
   Toast.makeText(getApplicationContext(),a,Toast.LENGTH_LONG).show();



}
}

小说.java

package org.apache.cordova.example;

import android.content.Context;
import android.content.Intent;
import android.telephony.*;
import android.app.Activity;
import android.os.Bundle;
import android.widget.Toast;

public class novel extends Activity
{ 
public int a=0;
public int getNumber()
{

    a=5;

 return a;
        }

}

我该如何解决？

Answer 1

你在 return block 之后使用了 intent 语句

返回电话号码 = tMgr.getLine1Number();

Intent myIntent = new Intent(novel.this, cordovaExample.class);

在返回 block 之后，任何代码都显示无法访问的错误。

传入intent参数后即可调用return。

   TelephonyManager tMgr=(TelephonyManager)mcontext.getSystemService(Context.TELEPHONY_SERVICE); 

   Intent intent = new Intent(this, cordovaExample.class);
   intent.putExtra("novel.PhoneNumber", PhoneNumber);
   startActivity(intent);
   return PhoneNumber = tMgr.getLine1Number();