package bjpkten.permissionrelateddemo;
import android.Manifest;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.widget.TextView;
import android.widget.Toast;
import java.security.Permission;
public class MainActivity extends AppCompatActivity {
private TextView mTextView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// setContentView(R.layout.activity_main);
mTextView = (TextView) findViewById(R.id.text);
}
@Override
protected void onResume() {
super.onResume();
mTextView.setText(R.string.app_name);
}
}
报错:
E/AndroidRuntime: FATAL EXCEPTION: main
Process: bjpkten.permissionrelateddemo, PID: 23988
java.lang.RuntimeException: Unable to resume activity {bjpkten.permissionrelateddemo/bjpkten.permissionrelateddemo.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(int)' on a null object reference
at android.app.ActivityThread.performResumeActivity(ActivityThread.java:3784)
at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:3816)
at android.app.servertransaction.ResumeActivityItem.execute(ResumeActivityItem.java:51)
at android.app.servertransaction.TransactionExecutor.executeLifecycleState(TransactionExecutor.java:145)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:70)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:193)
at android.app.ActivityThread.main(ActivityThread.java:6669)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(int)' on a null object reference
at bjpkten.permissionrelateddemo.MainActivity.onResume(MainActivity.java:37)
at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1412)
at android.app.Activity.performResume(Activity.java:7292)
at android.app.ActivityThread.performResumeActivity(ActivityThread.java:3776)
at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:3816)
at android.app.servertransaction.ResumeActivityItem.execute(ResumeActivityItem.java:51)
at android.app.servertransaction.TransactionExecutor.executeLifecycleState(TransactionExecutor.java:145)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:70)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:193)
at android.app.ActivityThread.main(ActivityThread.java:6669)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)