【Android -- 四大组件】一份四大组件开发学习指南

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）

使用 1. 闪退代码

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：

2. runOnUiThread() 使用

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();
            }
        });
    }
}