summary

I'm writing a program recently , The requirement is that the server-side program will constantly refresh the value of a field in the database , Then you need to write a client program to continuously read the field and display it on the interface . Here the database uses MySQL,Android Data interaction between client and server Volley frame .

Preparation

Volley yes Google Officially launched HTTP Method library , Use Volley The framework needs to be Android Studio Introduce the corresponding package , For details, please refer to my previous articles ：
Android Use Volley Frame for data transmission

Main code

The whole implementation logic is that the user clicks “START” after , Start to continuously pull the value of the corresponding field in the database , Also on UI Control . meanwhile , Set flag bit getAgain, Its meaning is as follows ：
getAgain = true： The current read operation has completed , Make the next read ;
getAgain = false：Volley The child thread is reading the value of the corresponding field in the database , The read operation is blocked .
The code is as follows ：
1. Variable bit declaration ：

public static boolean getAgain = true;

2.“START” Button Click event ：

mBtnBegin.setOnClickListener(new View.OnClickListener() {
    
            @Override
            public void onClick(View v) {
    
                // Start a loop refresh 
                new Thread(new Runnable() {
    
                    @Override
                    public void run() {
    
                        // Conduct 1000 Read operations 
                        for(int i = 0; i < 1000; ++i){
    
                            // Read the flag bit to judge 
                            if(getAgain){
    
                                // Enter the read state 
                                getAgain = false;
                                // Pull the latest field value from the database 
                                ShowMyCount(getApplicationContext(), LoginActivity.Username);
                                while (!getAgain){
    
                                    // Data reading , To block 
                                }
                            }
                        }
                    }
                }).start();
            }
        });

3.“ShowMyCount()” Method ：

Use Volley The framework interacts with the server. You can see the above article , For the functions to be realized in this paper , stay “ The query is successful ” Two statements need to be added to the statement block of ：

// The query is successful , to update UI Interface 
mTvCount.setText(count);
// The data reading is completed , Unblock state 
getAgain = true;

Optimize

1. Updated in this article UI The interface is directly in “ShowMyCount()” Method used in setText() Method , but Android In development ,UI The update of the interface usually uses Handler Mechanism .
2. In this paper, the for Cycle... Cycle 1000 Times to roughly realize automatic cyclic reading , But more than 1000 It will not be updated after UI Interface , There are two solutions ： Increase the number of cycles or use while loop .

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