java - 尝试遵循基本的如何将 Android 与 PHP、MySQL 教程连接起来 : application crashes - cannot import android. os.StrictMode

Question

好的 - 所以我正在使用以下教程:“如何将 Android 与 PHP、MySQL 连接”

然而，几乎所有尝试该教程的人(根据评论判断)都遇到了强制关闭问题，因为该应用程序仅设计为在 API 级别 8 或更早版本上运行。

一些用户为此开发了一个修复程序，涉及在 EditProductActivity.java 文件中添加以下代码行

//这部分只是为了确定将工作代码放在哪里

public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.edit_product);

//注意 * 在 EditProductActivity.java 的导入部分插入以下行//导入 android.os.StrictMode;

//现在是避免 NetworkOnMainThreadException 错误的代码

StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder()
.permitAll().build();
StrictMode.setThreadPolicy(policy);

但是，我在我的 logcat 中收到消息，指出 StrictMode 无法解析并且 StrictMode 无法解析为类型。我对此做了一些研究，并且 StrictMode 包含在 API 级别 8 及更高版本中。考虑到这一点，我将 AndroidManifest.xml 中的 API 级别提高到:

 <uses-sdk android:minSdkVersion="9"
          android:targetSdkVersion="9"/>

然后清理我的项目 - 但是我仍然得到 StrictMode cannot be resolved to a type 错误。

洛卡特:

    03-17 14:06:57.924: D/AndroidRuntime(18472): Shutting down VM
    03-17 14:06:57.924: W/dalvikvm(18472): threadid=1: thread exiting with uncaught exception (group=0x41604930)
    03-17 14:06:57.924: E/AndroidRuntime(18472): FATAL EXCEPTION: main
    03-17 14:06:57.924: E/AndroidRuntime(18472): java.lang.Error: Unresolved compilation problems: 
    03-17 14:06:57.924: E/AndroidRuntime(18472):    The import android.os.StrictMode cannot be resolved
   03-17 14:06:57.924: E/AndroidRuntime(18472):     StrictMode cannot be resolved to a type
    03-17 14:06:57.924: E/AndroidRuntime(18472):    StrictMode cannot be resolved to a type
    03-17 14:06:57.924: E/AndroidRuntime(18472):    StrictMode cannot be resolved
    03-17 14:06:57.924: E/AndroidRuntime(18472):    at com.example.androidhive.NewProductActivity.<init>(NewProductActivity.java:10)
    03-17 14:06:57.924: E/AndroidRuntime(18472):    at java.lang.Class.newInstanceImpl(Native Method)
    03-17 14:06:57.924: E/AndroidRuntime(18472):    at java.lang.Class.newInstance(Class.java:1319)
    03-17 14:06:57.924: E/AndroidRuntime(18472):    at android.app.Instrumentation.newActivity(Instrumentation.java:1054)
    03-17 14:06:57.924: E/AndroidRuntime(18472):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2097)
    03-17 14:06:57.924: E/AndroidRuntime(18472):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
    03-17 14:06:57.924: E/AndroidRuntime(18472):    at android.app.ActivityThread.access$600(ActivityThread.java:141)
    03-17 14:06:57.924: E/AndroidRuntime(18472):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234) 
    03-17 14:06:57.924: E/AndroidRuntime(18472):    at android.os.Handler.dispatchMessage(Handler.java:99)
    03-17 14:06:57.924: E/AndroidRuntime(18472):    at android.os.Looper.loop(Looper.java:137)
    03-17 14:06:57.924: E/AndroidRuntime(18472):    at android.app.ActivityThread.main(ActivityThread.java:5039)
    03-17 14:06:57.924: E/AndroidRuntime(18472):    at java.lang.reflect.Method.invokeNative(Native Method)
    03-17 14:06:57.924: E/AndroidRuntime(18472):    at java.lang.reflect.Method.invoke(Method.java:511)
    03-17 14:06:57.924: E/AndroidRuntime(18472):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
    03-17 14:06:57.924: E/AndroidRuntime(18472):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
    03-17 14:06:57.924: E/AndroidRuntime(18472):    at dalvik.system.NativeStart.main(Native Method)

Java:

import java.util.ArrayList;
import java.util.List;

import org.apache.http.NameValuePair;
import org.apache.http.message.BasicNameValuePair;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.os.StrictMode;

 public class EditProductActivity extends Activity {

EditText txtName;
EditText txtPrice;
EditText txtDesc;
EditText txtCreatedAt;
Button btnSave;
Button btnDelete;

String pid;

// Progress Dialog
private ProgressDialog pDialog;

// JSON parser class
JSONParser jsonParser = new JSONParser();

// single product url
private static final String url_product_detials =  "http://linkingmanager.zxq.net/get_product_details.php";

// url to update product
private static final String url_update_product = "http://linkingmanager.zxq.net/update_product.php";

// url to delete product
private static final String url_delete_product = "http://linkingmanager.zxq.net/delete_product.php";

// JSON Node names
private static final String TAG_SUCCESS = "success";
private static final String TAG_PRODUCT = "product";
private static final String TAG_PID = "pid";
private static final String TAG_NAME = "name";
private static final String TAG_PRICE = "price";
private static final String TAG_DESCRIPTION = "description";

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.edit_product);

    StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder()
    .permitAll().build();
    StrictMode.setThreadPolicy(policy);

    // save button
    btnSave = (Button) findViewById(R.id.btnSave);
    btnDelete = (Button) findViewById(R.id.btnDelete);

    // getting product details from intent
    Intent i = getIntent();

    // getting product id (pid) from intent
    pid = i.getStringExtra(TAG_PID);

    // Getting complete product details in background thread
    new GetProductDetails().execute();

    // save button click event
    btnSave.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View arg0) {
            // starting background task to update product
            new SaveProductDetails().execute();
        }
    });

    // Delete button click event
    btnDelete.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View arg0) {
            // deleting product in background thread
            new DeleteProduct().execute();
        }
    });

}

/**
 * Background Async Task to Get complete product details
 * */
class GetProductDetails extends AsyncTask<String, String, String> {

    /**
     * Before starting background thread Show Progress Dialog
     * */
    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        pDialog = new ProgressDialog(EditProductActivity.this);
        pDialog.setMessage("Loading product details. Please wait...");
        pDialog.setIndeterminate(false);
        pDialog.setCancelable(true);
        pDialog.show();
    }

    /**
     * Getting product details in background thread
     * */
    protected String doInBackground(String... params) {

        // updating UI from Background Thread
        runOnUiThread(new Runnable() {
            public void run() {
                // Check for success tag
                int success;
                try {
                    // Building Parameters
                    List<NameValuePair> params = new  ArrayList<NameValuePair>();
                    params.add(new BasicNameValuePair("pid", pid));

                    // getting product details by making HTTP request
                    // Note that product details url will use GET request
                    JSONObject json = jsonParser.makeHttpRequest(
                            url_product_detials, "GET", params);

                    // check your log for json response
                    Log.d("Single Product Details", json.toString());

                    // json success tag
                    success = json.getInt(TAG_SUCCESS);
                    if (success == 1) {
                        // successfully received product details
                        JSONArray productObj = json
                                 .getJSONArray(TAG_PRODUCT); // JSON Array

                        // get first product object from   JSON Array
                        JSONObject product = productObj.getJSONObject(0);

                        // product with this pid found
                        // Edit Text
                        txtName = (EditText) findViewById(R.id.inputName);
                        txtPrice = (EditText) findViewById(R.id.inputPrice);
                        txtDesc = (EditText)  findViewById(R.id.inputDesc);

                        // display product data in EditText
                          txtName.setText(product.getString(TAG_NAME));
                        txtPrice.setText(product.getString(TAG_PRICE));
                        txtDesc.setText(product.getString(TAG_DESCRIPTION));

                    }else{
                        // product with pid not found
                    }
                } catch (JSONException e) {
                    e.printStackTrace();
                }
            }
        });

        return null;
    }


    /**
     * After completing background task Dismiss the progress dialog
     * **/
    protected void onPostExecute(String file_url) {
        // dismiss the dialog once got all details
        pDialog.dismiss();
    }
}

/**
 * Background Async Task to  Save product Details
 * */
class SaveProductDetails extends AsyncTask<String, String, String> {

    /**
     * Before starting background thread Show Progress Dialog
     * */
    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        pDialog = new ProgressDialog(EditProductActivity.this);
        pDialog.setMessage("Saving product ...");
        pDialog.setIndeterminate(false);
        pDialog.setCancelable(true);
        pDialog.show();
    }

    /**
     * Saving product
     * */
    protected String doInBackground(String... args) {

        // getting updated data from EditTexts
        String name = txtName.getText().toString();
        String price = txtPrice.getText().toString();
        String description = txtDesc.getText().toString();

        // Building Parameters
        List<NameValuePair> params = new ArrayList<NameValuePair>();
        params.add(new BasicNameValuePair(TAG_PID, pid));
        params.add(new BasicNameValuePair(TAG_NAME, name));
        params.add(new BasicNameValuePair(TAG_PRICE, price));
        params.add(new BasicNameValuePair(TAG_DESCRIPTION, description));

        // sending modified data through http request
        // Notice that update product url accepts POST method
        JSONObject json = jsonParser.makeHttpRequest(url_update_product,
                "POST", params);

        // check json success tag
        try {
            int success = json.getInt(TAG_SUCCESS);

            if (success == 1) {
                // successfully updated
                Intent i = getIntent();
                // send result code 100 to notify about product update
                setResult(100, i);
                finish();
            } else {
                // failed to update product
            }
        } catch (JSONException e) {
            e.printStackTrace();
        }

        return null;
    }


    /**
     * After completing background task Dismiss the progress dialog
     * **/
    protected void onPostExecute(String file_url) {
        // dismiss the dialog once product uupdated
        pDialog.dismiss();
    }
}

/*****************************************************************
 * Background Async Task to Delete Product
 * */
class DeleteProduct extends AsyncTask<String, String, String> {

    /**
     * Before starting background thread Show Progress Dialog
     * */
    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        pDialog = new ProgressDialog(EditProductActivity.this);
        pDialog.setMessage("Deleting Product...");
        pDialog.setIndeterminate(false);
        pDialog.setCancelable(true);
        pDialog.show();
    }

    /**
     * Deleting product
     * */
    protected String doInBackground(String... args) {

        // Check for success tag
        int success;
        try {
            // Building Parameters
            List<NameValuePair> params = new ArrayList<NameValuePair>    (); 
            params.add(new BasicNameValuePair("pid", pid));

            // getting product details by making HTTP request
            JSONObject json = jsonParser.makeHttpRequest(
                    url_delete_product, "POST", params);

            // check your log for json response
            Log.d("Delete Product", json.toString());

            // json success tag
            success = json.getInt(TAG_SUCCESS);
            if (success == 1) {
                // product successfully deleted
                // notify previous activity by sending code 100
                Intent i = getIntent();
                // send result code 100 to notify about product deletion
                setResult(100, i);
                finish();
            }
        } catch (JSONException e) {
            e.printStackTrace();
        }

        return null;
    }

    /**
     * After completing background task Dismiss the progress dialog
     * **/
    protected void onPostExecute(String file_url) {
        // dismiss the dialog once product deleted
        pDialog.dismiss();

    }

}
}

Answer 1

StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder()
.permitAll().build();
StrictMode.setThreadPolicy(policy);

由于您使用的是 AsyncTask无需设置 ThreadPolicy .并且不要忘记 StrictMode 从 2.3 版本开始可用。

更新:

您的应用没有指定好。看看这个

protected String doInBackground(String... params) {

        runOnUiThread(new Runnable() { 
           ...
           txtName = (EditText) findViewById(R.id.inputName);
           txtPrice = (EditText) findViewById(R.id.inputPrice);
           txtDesc = (EditText)  findViewById(R.id.inputDesc);

           // display product data in EditText
           txtName.setText(product.getString(TAG_NAME));
           txtPrice.setText(product.getString(TAG_PRICE));
           txtDesc.setText(product.getString(TAG_DESCRIPTION));
           ...
        }
}

你为什么要这样做？ doInBackground()直接设计用于执行后台操作也已经在后台线程上运行，您不应该从中执行 UI 更新。你不应该混合它。

如果你想更新用户界面，AsyncTask提供了实现它的适当方法:

• onPreExecute()
• onProgressUpdate()
• onPostExecute()

因此，如果您想使用有关后台任务调用进度的一些信息来更新您的 UI publishProgress(<data>)自动调用 onProgressUpdate() 的方法方法及其更新 UI。

在您的情况下，您正在执行 UI 的初始化doInBackground() 中的元素您不应该使用的方法。

我建议你这样做:

1. 在 onCreate() 中初始化您的小部件方法。
2. 当你想用从中检索到的数据更新它们时 doInBackground()方法，调用 publishProgress()调用 onProgressUpdate()方法并在这里执行更新

例子如下:

@Override
protected void onProgressUpdate(String... params) {
   txtName.setText(<value>);
   ...
}

根据上面提到的事情，我猜你需要阅读 AsyncTask 教程:

• > So check thislink