安卓Socket 與esp8266 通信 錯誤
#在點擊按鈕發送資料時出現了如下錯誤：
小白求助！
按下按鈕錯誤提示：
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.mywifi.tyf.cn.wifi2, PID: 8143
java.lang.NullPointerException: Attempt to invoke virtual method ‘void java.io.BufferedWriter.write(java.lang.String)’ on a null object reference
at com.mywifi.tyf.cn.wifi2.MainActivity2.onClick(MainActivity.java:63)atandroid.view.View.performClick(View.java:5637)atandroid.view.View2.onClick(MainActivity.java:63)at android.view.View.performClick(View.java:5637)at android.view.View2.onClick(MainActivity.java:63)atandroid.view.View.performClick(View.java:5637)atandroid.view.ViewPerformClick.run(View.java:22429)
at android.os.Handler.handleCallback(Handler.java:751)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
源代碼
public class MainActivity extends Activity{
private EditText IP,Port;
private Button Link,Butt1,Butt2;
private Socket socket =null;
private BufferedWriter writer = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
IP = (EditText)findViewById(R.id.ip);
Port = (EditText)findViewById(R.id.port);
Link = (Button)findViewById(R.id.link);
Butt1 = (Button)findViewById(R.id.butt1);
Butt2 = (Button)findViewById(R.id.butt2);
Link.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if(socket == null) {
String ip = IP.getText().toString();
int port = Integer.valueOf(Port.getText().toString());
MyThread myThread = new MyThread(ip,port);
myThread.start();
}if(socket != null){
try{
socket.close();
socket=null; // 清空mSocket
Link.setText(“連接”);
Toast.makeText(MainActivity.this,“連接已關閉”,Toast.LENGTH_LONG).show();
}catch (IOException e){
e.printStackTrace();
}
}
}
});
/開/
Butt1.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// ThreadSendData(“0”);
try {
writer.write(0+"\n");
writer.flush();
} catch (IOException e) {
e.printStackTrace();
}
Toast.makeText(MainActivity.this, “發送成功”, Toast.LENGTH_SHORT).show();
}
});
//關
Butt2.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
ThreadSendData(“1”);
Toast.makeText(MainActivity.this, “發送成功”, Toast.LENGTH_SHORT).show();
}
});
}
/*連接執行緒/
private class MyThread extends Thread{
private String ip;
private int port;
public MyThread(String ip,int port) {
this.ip = ip;
this.port = port;
}
public void run(){
try {
socket = new Socket(ip,port);
writer = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream()));
Toast.makeText(MainActivity.this, “發送成功”, Toast.LENGTH_SHORT).show();
runOnUiThread(new Runnable() {
@Override
public void run() {
Link.setText(“已連接”);
Toast.makeText(MainActivity.this, “已連接”, Toast.LENGTH_SHORT).show();
}
});
} catch (IOException e) {
e.printStackTrace();
runOnUiThread(new Runnable() {
@Override
public void run() {
Toast.makeText(MainActivity.this, “連接失敗”, Toast.LENGTH_SHORT).show();
}
});
}
}
}
/*用于發送資料/
public void ThreadSendData(String num){
try {
writer.write(num+"\n");
writer.flush();
} catch (IOException e) {
e.printStackTrace();
}
}
}
請大神幫忙指點哈，搜了很多資料也沒找到頭緒。
文章最后發布于: 2019-11-23
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