我的代码出了什么问题？当我尝试在设备上运行应用程序时，它会停止工作并显示应用程序停止工作的通知。
package lv.kvsol.atminivietu;
import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Intent;
import android.content.IntentSender.SendIntentException;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Toast;
import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.GooglePlayServicesClient.ConnectionCallbacks;
import com.google.android.gms.common.GooglePlayServicesClient.OnConnectionFailedListener;
import com.google.android.gms.common.Scopes;
import com.google.android.gms.plus.PlusClient;
public class MainActivity extends Activity implements View.OnClickListener,
ConnectionCallbacks, OnConnectionFailedListener {
private static final String TAG = "MainActivity";
private static final int REQUEST_CODE_RESOLVE_ERR = 9000;
private ProgressDialog mConnectionProgressDialog;
private PlusClient mPlusClient;
private ConnectionResult mConnectionResult;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
findViewById(R.id.sign_in_button).setOnClickListener(this);
mPlusClient = new PlusClient.Builder(this, this, this)
.setActions("http://schemas.google.com/AddActivity", "http://schemas.google.com/BuyActivity")
.setScopes(Scopes.PLUS_LOGIN) // recommended login scope for social features
// .setScopes("profile") // alternative basic login scope
.build();
// Progress bar to be displayed if the connection failure is not resolved.
mConnectionProgressDialog = new ProgressDialog(this);
mConnectionProgressDialog.setMessage("Signing in...");
}
@Override
protected void onStart() {
super.onStart();
mPlusClient.connect();
}
@Override
protected void onStop() {
super.onStop();
mPlusClient.disconnect();
}
@Override
public void onConnectionFailed(ConnectionResult result) {
if (mConnectionProgressDialog.isShowing()) {
// The user clicked the sign-in button already. Start to resolve
// connection errors. Wait until onConnected() to dismiss the
// connection dialog.
if (result.hasResolution()) {
try {
result.startResolutionForResult(this, REQUEST_CODE_RESOLVE_ERR);
} catch (SendIntentException e) {
mPlusClient.connect();
}
}
}
// Save the result and resolve the connection failure upon a user click.
mConnectionResult = result;
}
@Override
protected void onActivityResult(int requestCode, int responseCode, Intent intent) {
if (requestCode == REQUEST_CODE_RESOLVE_ERR && responseCode == RESULT_OK) {
mConnectionResult = null;
mPlusClient.connect();
}
}
@Override
public void onConnected(Bundle connectionHint) {
String accountName = mPlusClient.getAccountName();
Toast.makeText(this, accountName + " is connected.", Toast.LENGTH_LONG).show();
}
@Override
public void onClick(View view) {
if (view.getId() == R.id.sign_in_button && !mPlusClient.isConnected()) {
if (mConnectionResult == null) {
mConnectionProgressDialog.show();
} else {
try {
mConnectionResult.startResolutionForResult(this, REQUEST_CODE_RESOLVE_ERR);
} catch (SendIntentException e) {
// Try connecting again.
mConnectionResult = null;
mPlusClient.connect();
}
}
}
}
@Override
public void onDisconnected() {
Log.d(TAG, "disconnected");
}
}
有我的git repo：https://github.com/kvergins/AtminiVietu
有日志文件：
01-20 21:38:30.350: W/asset(29993): Copying FileAsset 0x594481f0 (zip:/data/app/lv.kvsol.atminivietu-1.apk:/resources.arsc) to buffer size 142428 to make it aligned.
01-20 21:38:30.815: W/dalvikvm(29993): threadid=1: thread exiting with uncaught exception (group=0x41d67a08)
01-20 21:38:30.825: E/AndroidRuntime(29993): FATAL EXCEPTION: main
01-20 21:38:30.825: E/AndroidRuntime(29993): java.lang.RuntimeException: Unable to start activity ComponentInfo{lv.kvsol.atminivietu/lv.kvsol.atminivietu.MainActivity}: java.lang.NullPointerException
01-20 21:38:30.825: E/AndroidRuntime(29993): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2463)
01-20 21:38:30.825: E/AndroidRuntime(29993): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2520)
01-20 21:38:30.825: E/AndroidRuntime(29993): at android.app.ActivityThread.access$600(ActivityThread.java:162)
01-20 21:38:30.825: E/AndroidRuntime(29993): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1366)
01-20 21:38:30.825: E/AndroidRuntime(29993): at android.os.Handler.dispatchMessage(Handler.java:99)
01-20 21:38:30.825: E/AndroidRuntime(29993): at android.os.Looper.loop(Looper.java:158)
01-20 21:38:30.825: E/AndroidRuntime(29993): at android.app.ActivityThread.main(ActivityThread.java:5751)
01-20 21:38:30.825: E/AndroidRuntime(29993): at java.lang.reflect.Method.invokeNative(Native Method)
01-20 21:38:30.825: E/AndroidRuntime(29993): at java.lang.reflect.Method.invoke(Method.java:511)
01-20 21:38:30.825: E/AndroidRuntime(29993): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1083)
01-20 21:38:30.825: E/AndroidRuntime(29993): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:850)
01-20 21:38:30.825: E/AndroidRuntime(29993): at dalvik.system.NativeStart.main(Native Method)
01-20 21:38:30.825: E/AndroidRuntime(29993): Caused by: java.lang.NullPointerException
01-20 21:38:30.825: E/AndroidRuntime(29993): at lv.kvsol.atminivietu.MainActivity.onCreate(MainActivity.java:31)
01-20 21:38:30.825: E/AndroidRuntime(29993): at android.app.Activity.performCreate(Activity.java:5165)
01-20 21:38:30.825: E/AndroidRuntime(29993): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1103)
01-20 21:38:30.825: E/AndroidRuntime(29993): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2419)
01-20 21:38:30.825: E/AndroidRuntime(29993): ... 11 more
01-20 21:38:30.910: D/Process(29993): killProcess, pid=29993
01-20 21:38:30.935: D/Process(29993): dalvik.system.VMStack.getThreadStackTrace(Native Method)
01-20 21:38:30.935: D/Process(29993): java.lang.Thread.getStackTrace(Thread.java:599)
01-20 21:38:30.935: D/Process(29993): android.os.Process.killProcess(Process.java:1004)
01-20 21:38:30.935: D/Process(29993): com.android.internal.os.RuntimeInit$UncaughtHandler.uncaughtException(RuntimeInit.java:123)
01-20 21:38:30.935: D/Process(29993): java.lang.ThreadGroup.uncaughtException(ThreadGroup.java:693)
01-20 21:38:30.935: D/Process(29993): java.lang.ThreadGroup.uncaughtException(ThreadGroup.java:690)
01-20 21:38:30.935: D/Process(29993): dalvik.system.NativeStart.main(Native Method)
答案 0 :(得分：2)
findViewById(R.id.sign_in_button)将返回null，因为您尚未使用setContentView设置布局。这就是你在logcat中得到NullpointerException的原因。