java - 如果目标操作失败，如何在按钮中显示警报对话框

Question

我正在尝试创建一个应用程序，用户可以在其中拍照并将其设置为壁纸。现在，当我单击按钮并返回而不拍照并单击设置壁纸时，我想显示一个警报对话框。我未启动图像采集时可以设置，但启动但未采集图像时则不能设置

package com.sagarapp;

import java.io.IOException;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.graphics.Bitmap;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.ImageButton;
import android.widget.ImageView;

public class Camera extends Activity implements View.OnClickListener{

ImageView img;
ImageButton takepic;
Button setdp;
Intent i;
final static int cameraData = 0;
Bitmap bmp;
final Context context = this;
boolean taken = false;

@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.photo);
    initialize();
    takepic.setOnClickListener(this);
    setdp.setOnClickListener(this);

}

private void initialize() {
    // TODO Auto-generated method stub
    img = (ImageView)findViewById(R.id.Ivpic);
    takepic = (ImageButton)findViewById(R.id.Ibcapture);
    setdp = (Button)findViewById(R.id.Bsetdp);
}

@SuppressWarnings("deprecation")
@Override
public void onClick(View v) {
    // TODO Auto-generated method stub
    switch(v.getId())
    {
    case R.id.Ibcapture:
        i = new Intent(android.provider.MediaStore.ACTION_IMAGE_CAPTURE);
        taken = true;
        startActivityForResult(i,cameraData);
        break;
    case R.id.Bsetdp:
        try {
            if(taken)
                getApplicationContext().setWallpaper(bmp);
            else{
            AlertDialog.Builder alertDialogBulider = new AlerDialog.Builder(context);
            alertDialogBulider.setTitle("Warning!");
            alertDialogBulider.setMessage("No Image Is Available");
            alertDialogBulider.setCancelable(false);
  alertDialogBulider.setNeutralButton("OK", new   DialogInterface.OnClickListener()   {

                @Override
                public void onClick(DialogInterface dialog, int id) {
                    // TODO Auto-generated method stub
                    dialog.cancel();
                }
            });
            AlertDialog alertDialog = alertDialogBulider.create();
            alertDialog.show();
            }
        } catch (IOException e) {
            // TODO Auto-generated catch block

            e.printStackTrace();
        }
        break;
    }
}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    // TODO Auto-generated method stub
    super.onActivityResult(requestCode, resultCode, data);
    if(resultCode == RESULT_OK)
    {
        Bundle extras = data.getExtras();
        bmp = (Bitmap)extras.get("data");
        img.setImageBitmap(bmp);
    }
    else
    {
        AlertDialog.Builder alertDialogBulider = new AlertDialog.Builder(context);
        alertDialogBulider.setTitle("Warning!");
        alertDialogBulider.setMessage("No Photo Is Taken");
        alertDialogBulider.setCancelable(false);
        alertDialogBulider.setNeutralButton("OK", new DialogInterface.OnClickListener() {

            @Override
            public void onClick(DialogInterface dialog, int id) {
                // TODO Auto-generated method stub
                dialog.cancel();
            }
        });
        AlertDialog alertDialog = alertDialogBulider.create();
        alertDialog.show();

    }
}
}

Answer 1

只有在 onActivityResult() 中收到 RESULT_OK 结果代码时，您的 taken boolean 变量才应设置为 true > 方法。这意味着用户实际上拍摄了照片并保存了它。从 R.id.Ibcapture View onClick () 方法中删除它。