android.view.WindowManager$BadTokenException: Unable to add window

转载请注明出处： https://blog.****.net/u011038298/article/details/84104451 

import android.app.AlertDialog;
import android.content.DialogInterface;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
import android.view.View;


public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        findViewById(R.id.btn_dialog).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                showDialog();
            }
        });
    }

    private void showDialog() {
        /**
         * 这里不能使用getApplicationContext()，否则会报错。
         * 要传入当前Activity来添加这个窗体，将getApplicationContext()改成this即可
         */
        new AlertDialog.Builder(getApplicationContext())
                .setIcon(android.R.drawable.ic_dialog_info)
                .setTitle("演示")
                .setPositiveButton("确定", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialogInterface, int i) {
                    }
                }).setNegativeButton("取消", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialogInterface, int i) {
            }
        }).create().show();
    }

}

报错信息如下：