Question

java.lang.ClassCastException：android.app.Application无法强制转换为com.example.project.DataDevice

我的代码：

public class Project extends Activity{

private boolean connection = false;
public Tag tagFromIntent = null;

private Button textRead;
private NFCForegroundUtil nfcForegroundUtil;



@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.project);    

    nfcForegroundUtil = new NFCForegroundUtil(this);

    this.textRead= (Button) findViewById(R.id.button2);

    initListeners();
}


private void initListeners() {


    textRead.setOnClickListener(new OnClickListener()
    {

        public void onClick(View v)
        {

            if (connection == true)
            {
                DataDevice dataDevice = (DataDevice) getApplication();
                dataDevice.setCurrentTag(tagFromIntent);

                IsoDep nfca = IsoDep.get(dataDevice.getCurrentTag());

                try
                {
                    byte[] read= new byte[] { 0x00};

                    byte[] ans = null;

                    nfca.setTimeout(2000);
                    nfca.connect();
                    nfca.setTimeout(2000);
                    if (nfca.isConnected())
                    {

                        nfca.setTimeout(2000);
                        ans = nfca.transceive(read);

                        try
                        {
                            Thread.sleep(1500);
                        }
                        catch (InterruptedException e)
                        {
                            e.printStackTrace();
                        }

                    }

                    nfca.close();
                    String textRead = HexBin.encode(ans);

                }

                catch (IOException e)
                {
                    Log.i("A", "IOException is: " + e.getMessage());
                    e.printStackTrace();
                }

                if (nfca.isConnected())
                {
                    try
                    {
                        nfca.close();
                    }
                    catch (IOException e)
                    {
                        e.printStackTrace();
                    }
                }

            }

        }
    });


}

@Override
protected void onNewIntent(Intent intent)
{

    super.onNewIntent(intent);
    action = intent.getAction();
    tagFromIntent = intent.getParcelableExtra(NfcAdapter.EXTRA_TAG);
    connection = true;

}

public void onPause()
{
    super.onPause();
    nfcForegroundUtil.disableForeground();
}

public void onResume()
{
    super.onResume();

    nfcForegroundUtil.enableForeground();

    if (!nfcForegroundUtil.getNfc().isEnabled())
    {
        Toast.makeText(
                getApplicationContext(),
                "Please activate NFC and press Back to return to the application!",
                Toast.LENGTH_LONG).show();
        startActivity(new Intent(
                android.provider.Settings.ACTION_WIRELESS_SETTINGS));
    }
}
}

我的清单代码：

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.project"
android:versionCode="1"
android:versionName="1.0" >

<uses-sdk
    android:minSdkVersion="8"
    android:targetSdkVersion="15" />

<uses-permission android:name="android.permission.NFC" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

<uses-feature
    android:name="android.hardware.nfc"
    android:required="true" />

<application
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme" 
    android:name="android.app.Application"> 
    <activity
        android:name=".StartActivity"
        android:label="@string/title_activity_main" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.DEFAULT" />
            <action android:name="android.nfc.action.TECH_DISCOVERED" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>

    <activity 
        android:screenOrientation="portrait" 
        android:name=".Project" 
        android:label="@string/title_activity_main" />

</application>

我的错误：

FATAL EXCEPTION: main
java.lang.ClassCastException: android.app.Application cannot be cast to com.example.Project.DataDevice
at com.example.project.Project$1.onClick(Project.java:67)
at android.view.View.performClick(View.java:3511)
at android.view.View$PerformClick.run(View.java:14105)
at android.os.Handler.handleCallback(Handler.java:605)
at android.os.Handler.dispatchMessage(Handler.java:92)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:4424)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
at dalvik.system.NativeStart.main(Native Method)

DataDevice类：

public class DataDevice extends Application
{
    private Tag currentTag;

    public void setCurrentTag(Tag currentTag) {
        this.currentTag = currentTag;
    }

    public Tag getCurrentTag() {
        return currentTag;
    }

    //(...)
}

我在stackOverflow上寻找答案，没有任何帮助。谁知道发生了什么？ DataDevice和NFCUtilForeground运行良好（在其他应用程序中）。

Answer 1

清单文件中android:name标记中的application属性应指向您的DataDevice类。像：

<application
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" 
android:name="your.package.DataDevice">

.........
..........
</application>

java.lang.ClassCastException：android.app.Application - cast

1 个答案: