java - (Android Java Sqlite)由于IP地址导致连接数据库失败时如何提示toast

Question

如果成功插入数据库，则 toast 消息有效，但如果例如我更改为无效的主机 IP 地址，则不会显示“无法创建配置文件”toast 消息

这是我的代码:

public class RegistrationActivity extends AppCompatActivity implements onTaskCompleted {

Spinner greetingSpinner = null;
EditText edit_Name = null;

// TAG for debug log message
private final String TAG = this.getClass().getSimpleName();
// Declare variables for profile and response
String name;
String greeting;
String id;
String status;
String msgType;
private static final String REQ_UPLOAD = "1001";
private static final String REQ_DOWNLOAD = "1002";

// Set host address of the WAMP Server
public static final String HOST = "192.168.1.1";
// Set virtual directory of the host website
public static final String DIR = "myproject";

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

    greetingSpinner = (Spinner) findViewById(R.id.spinner_greeting);
    edit_Name = (EditText) findViewById(R.id.edit_name);
}

/*public void onNextActivityClicked(View view)
{
    saveAsPreferences();
    Toast toast = Toast.makeText(this, "Profile created \n successfully!", Toast.LENGTH_SHORT);
    TextView v = (TextView) toast.getView().findViewById(android.R.id.message);
    if( v != null) v.setGravity(Gravity.CENTER);
    toast.setGravity(Gravity.CENTER, 0, 0);
    ViewGroup group = (ViewGroup) toast.getView();
    TextView messageTextView = (TextView) group.getChildAt(0);
    messageTextView.setTextSize(25);
    toast.show();
    new Handler().postDelayed(new Runnable() {
        @Override
        public void run() {
            startActivity(new Intent(RegistrationActivity.this, MainActivity.class));
        }
    }, 2000);

}*/

// Convert profile information to JSON string
public String convertToJSON() {
    JSONStringer jsonText = new JSONStringer();
    try {
        jsonText.object();
        jsonText.key("type");
        jsonText.value(msgType);
        jsonText.key("greeting");
        jsonText.value(greeting);
        jsonText.key("name");
        jsonText.value(name);
        jsonText.key("id");
        jsonText.value(id);
        jsonText.endObject();
    } catch (Exception e) {
        e.printStackTrace();
    }
    return jsonText.toString();
}

// Retrieve profile information from JSON string
public void retrieveFromJSON(String message) {
    try {
        if(id != null) {
            JSONObject jsonObject = new JSONObject(message);
            msgType = jsonObject.getString("type");
            if (msgType.equals(REQ_DOWNLOAD)) {
                name = jsonObject.getString("name");
                greeting = jsonObject.getString("greeting");
            }
         else if(id.equals(null)){
                Toast toast = Toast.makeText(this, "Profile creation failed, \n please try again later!", Toast.LENGTH_SHORT);
                TextView v = (TextView) toast.getView().findViewById(android.R.id.message);
                if (v != null) v.setGravity(Gravity.CENTER);
                toast.setGravity(Gravity.CENTER, 0, 0);
                ViewGroup group = (ViewGroup) toast.getView();
                TextView messageTextView = (TextView) group.getChildAt(0);
                messageTextView.setTextSize(25);
                toast.show();
            }
        }
    } catch (Exception e) {
        e.printStackTrace();
    }
}

// Handler for upload button click event
public void onNextActivityClicked(View v) {
// convert edit text values to string data
    msgType = REQ_UPLOAD;
    Spinner etGreeting = (Spinner) findViewById(R.id.spinner_greeting);
    greeting = etGreeting.getSelectedItem().toString();
    EditText etName = (EditText) findViewById(R.id.edit_name);
    name = etName.getText().toString();
// create data in JSON format
    String jsonString = convertToJSON();
// call AsyncTask to perform network operation on separate thread
    HttpAsyncTask task = new HttpAsyncTask(this);
    task.execute("http://" + HOST + "/" + DIR + "/registerProfile.php", jsonString);
}


// Handler for HTTPAsyncTask complete event
@Override
public void onTaskCompleted(String response) {
// retrieve response information from JSON
    retrieveFromJSON(response);
// if response is from upload request
    if (msgType.equals(REQ_UPLOAD)) {
        SharedPreferences profile = getSharedPreferences("preferences", MODE_PRIVATE);
        SharedPreferences.Editor editor = profile.edit();
        editor.putString("name", name);
        editor.putString("greeting", greeting);
        editor.commit();

        Toast toast = Toast.makeText(this, "Profile created \n successfully!", Toast.LENGTH_SHORT);
        TextView v = (TextView) toast.getView().findViewById(android.R.id.message);
        if (v != null) v.setGravity(Gravity.CENTER);
        toast.setGravity(Gravity.CENTER, 0, 0);
        ViewGroup group = (ViewGroup) toast.getView();
        TextView messageTextView = (TextView) group.getChildAt(0);
        messageTextView.setTextSize(25);
        toast.show();

        new Handler().postDelayed(new Runnable() {
            @Override
            public void run() {
                startActivity(new Intent(RegistrationActivity.this, MainActivity.class));
            }
        }, 2000);
    }
}

Answer 1

我不知道确切的代码，但尝试连接时应该会出现异常。异常名称为UnknownHostException。您可以在连接逻辑周围放置 try catch，如果您遇到上述异常，那么它一定是由于 ip cahnge 而您可以处理它。