当我调用另一个意图时出错
我无法解决此问题，因此我需要尽快解决它，以完成课程的完成工作。预先感谢您的任何帮助！
06-09 14:41:28.902: E/AndroidRuntime(769): FATAL EXCEPTION: main
06-09 14:41:28.902: E/AndroidRuntime(769): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{br.com.projeto_tcc/br.com.projeto_tcc.view.EscolhaGUI}: java.lang.NullPointerException
06-09 14:41:28.902: E/AndroidRuntime(769):
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2106)
06-09 14:41:28.902: E/AndroidRuntime(769):
我的清单
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="br.com.projeto_tcc"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="17" />
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN"/>
<uses-permission android:name="android.permission.BLUETOOTH"/>
<uses-permission android:name="android.permission.WRITE_INTERNAL_STORAGE" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="br.com.projeto_tcc.view.NewPlayerGUI"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name="br.com.projeto_tcc.view.PlayerGUI"/>
<activity android:name="br.com.projeto_tcc.view.OpcaoGUI"/>
<activity android:name="br.com.projeto_tcc.view.JogoGUI"/>
<activity android:name="br.com.projeto_tcc.view.EscolhaGUI"/>
<activity android:name="br.com.projeto_tcc.bluetooth.Actv"/>
<activity android:name="br.com.projeto_tcc.bluetooth.MainActivity"/>
</application>
</manifest>
我的课
public class EscolhaGUI extends Activity {
Intent intent = new Intent(this, Actv.class);
Intent intent2 = new Intent(this, MainActivity.class);
@Override
protected void onCreate(Bundle savedInstanceState) {
try {
final Button btn_esp = (Button) findViewById(R.id.btn_esp);
final Button btn_conv = (Button) findViewById(R.id.btn_conv);
super.onCreate(savedInstanceState);
setContentView(R.layout.escolher);
btn_esp.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View arg0) {
finish();
startActivity(intent);
}
});
btn_conv.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View arg0) {
finish();
startActivity(intent2);
}
});
} catch (Exception e) {
AlertDialog alertDialog;
alertDialog = new AlertDialog.Builder(this).create();
alertDialog.setTitle("Erro");
alertDialog.setMessage("Este: ." + e);
alertDialog.show();
}
}
最佳答案
您遇到的问题是在调用setContentView(R.layout.escolher)之前要检索这些按钮。因此，在findViewById之后放置对setContentView的调用，您的onCreate方法应如下所示：
@Override
protected void onCreate(Bundle savedInstanceState) {
try {
super.onCreate(savedInstanceState);
setContentView(R.layout.escolher);
final Button btn_esp = (Button) findViewById(R.id.btn_esp);
final Button btn_conv = (Button) findViewById(R.id.btn_conv);
btn_esp.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View arg0) {
finish();
startActivity(intent);
}
});
btn_conv.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View arg0) {
finish();
startActivity(intent2);
}
});
} catch (Exception e) {
AlertDialog alertDialog;
alertDialog = new AlertDialog.Builder(this).create();
alertDialog.setTitle("Erro");
alertDialog.setMessage("Este: ." + e);
alertDialog.show();
}
}
编辑：
如果您不太清楚我要说的是什么，请尝试调试。您可以打赌，两个按钮都等于null，从而在此行中引起NPE：
btn_esp.setOnClickListener(new OnClickListener() {...}
就像logcat跟踪在这里指出的那样：
06-09 14:41:28.902: E/AndroidRuntime(769): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{br.com.projeto_tcc/br.com.projeto_tcc.view.EscolhaGUI}: java.lang.NullPointerException