简介
不能在主线程以外操作 UI,Android 中把耗时的操作都放到子线程里面,主线程又叫 UI 线程。
注意:
- 不要阻塞主线程( UI 线程)
- 不要从主线程以外的线程更新 UI( UI 线程)
public class MainActivity extends AppCompatActivity {
private TextView mTextView;
@SuppressLint("MissingInflatedId")
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mTextView = findViewById(R.id.tv_text);
mTextView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
new Thread(new Runnable() {
@Override
public void run() {
try {
Thread.sleep(5000);
}catch (InterruptedException e){
e.printStackTrace();
}
Toast.makeText(MainActivity.this,"click hello",Toast.LENGTH_SHORT).show();
}
}).start();
}
});
}
}
运行结果:
public class MainActivity extends AppCompatActivity {
private TextView mTextView;
@SuppressLint("MissingInflatedId")
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mTextView = findViewById(R.id.tv_text);
mTextView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
new Thread(new Runnable() {
@Override
public void run() {
try {
Thread.sleep(5000);
}catch (InterruptedException e){
e.printStackTrace();
}
runOnUiThread(new Runnable() {
@Override
public void run() {
Toast.makeText(MainActivity.this,"click hello",Toast.LENGTH_SHORT).show();
}
});
}
}).start();
}
});
}
}
这次程序运行正常,点击 Hello Word,五秒以后,正确弹出吐司。
3. View.post()使用 控件.post 的方式,把消息传递到主线程中
public class MainActivity extends AppCompatActivity {
private TextView mTextView;
@SuppressLint("MissingInflatedId")
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mTextView = findViewById(R.id.tv_text);
mTextView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
new Thread(new Runnable() {
@Override
public void run() {
try {
Thread.sleep(5000);
}catch (InterruptedException e){
e.printStackTrace();
}
mTextView.post(new Runnable() {
@Override
public void run() {
Toast.makeText(MainActivity.this,"click hello",Toast.LENGTH_SHORT).show();
}
});
}
}).start();
}
});
}
}
4. Thread + Handler
这是最经典的一种实现方式,扩展性好,使用广泛。
public class MainActivity extends AppCompatActivity {
private TextView mTextView;
//这个地方的handler最好封装 防止内存泄漏
private Handler handler = new Handler() {
@Override
public void handleMessage(Message msg) {
if (msg.what == 100) {
String res = (String) msg.obj;
mTextView.setText(res);
Toast.makeText(getApplicationContext(), res, Toast.LENGTH_SHORT).show();
}
}
};
@SuppressLint("MissingInflatedId")
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mTextView = findViewById(R.id.tv_text);
mTextView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
new Thread(new Runnable() {
@Override
public void run() {
try {
Thread.sleep(5000);
}catch (InterruptedException e){
e.printStackTrace();
}
Message msg = new Message();
msg.what = 100; //消息发送的标志
msg.obj = "text click button"; //消息发送的内容
handler.sendMessage(msg);
}
}).start();
}
});
}
}