Android-Handler在主线程和子线程中demo

ゝ一世哀愁。 2022-10-15 09:00 200阅读 0赞

一、Handler  
1、Handler写在主线程中

public class HandlerActivity extends Activity { 
        private ImageView imagChange;
        // 定义切换的图片数组id
        int imgids[] = new int[]{ 
                R.drawable.ic_pikachu1, R.drawable.ic_pikachu2,
                R.drawable.ic_pikachu3, R.drawable.ic_pikachu4
        };
        int imgStart = 0;
        Handler handler = new Handler() { 
            @Override
            //重写handleMessage方法,根据msg中what的值判断是否执行后续操作
            public void handleMessage(@NonNull Message msg) { 
                super.handleMessage(msg);
                if (msg.what == 0x110) { 
                    imagChange.setImageResource(imgids[imgStart++ % 4]);
                }
            }
        };
    
        @Override
        protected void onCreate(@Nullable Bundle savedInstanceState) { 
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_handler);
            imagChange = findViewById(R.id.img);
    
            //使用定时器,每隔200毫秒让handler发送一个空信息
            new Timer().schedule(new TimerTask() { 
                @Override
                public void run() { 
                    handler.sendEmptyMessage(0x110);
                }
            }, 0, 200);
        }
    }

效果：定时切换图片  
2、Handler写在子线程中,由主线程给子线程发送消息  
输入一个数，计算质数

public class HandleActivity extends Activity { 
        static final String UPPER_NUM = "upper";
        EditText mEtNum;
        CalThread calThread;
    
        // 定义一个线程类
        class CalThread extends Thread { 
            public Handler mHandler;
    
            public void run() { 
                Looper.prepare();
                mHandler = new Handler() { 
                    @Override
                    public void handleMessage(@NonNull Message msg) { 
                        super.handleMessage(msg);
                        if (msg.what == 0x120) { 
                            int upper = msg.getData().getInt(UPPER_NUM);
                            List<Integer> nums = new ArrayList<Integer>();
                            // 计算从2开始、到upper的所有质数
                            outer:
                            for (int i = 2; i <= upper; i++) { 
                                // 用i处于从2开始、到i的平方根的所有数
                                for (int j = 2; j <= Math.sqrt(i); j++) { 
                                    // 如果可以整除，表明这个数不是质数
                                    if (i != 2 && i % j == 0) { 
                                        continue outer;
                                    }
                                }
                                nums.add(i);
                                // Toast.makeText(HandleActivity.this, "质数分别为：" + nums.toString(), Toast.LENGTH_SHORT).show();
                            }
                            Log.d("Handler.class", "质数分别为：" + nums.toString());
                        }
                    }
                };
                Looper.loop();
            }
        }
    
        @Override
        protected void onCreate(@Nullable Bundle savedInstanceState) { 
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_headle);
            mEtNum = findViewById(R.id.etNum);
            calThread = new CalThread();
            // 启动新线程
            calThread.start();
        }
    
        // 为按钮的点击事件提供事件处理函数
        public void cal(View view) { 
            // 创建消息
            Message msg = new Message();
            msg.what = 0x120;
            Bundle bundle = new Bundle();
            bundle.putInt(UPPER_NUM, Integer.parseInt(mEtNum.getText().toString()));
            msg.setData(bundle);
            // 向新线程中的Handler发送消息
            calThread.mHandler.sendMessage(msg);
        }
    }

输入数字16，结果如下显示：  
![在这里插入图片描述][20210524160910534.png]  
加强版，更新UI对应控件，再次由子线程向主线程中发送消息

public class HandleActivity extends Activity { 
        static final String UPPER_NUM = "upper";
        public Handler mainHandler;
        private EditText mEtNum;
        private TextView mTest;
        CalThread calThread;
    
        // 定义一个线程类
        class CalThread extends Thread { 
            public Handler mHandler;
    
            public void run() { 
                Looper.prepare();
                mHandler = new Handler() { 
                    @Override
                    public void handleMessage(@NonNull Message msg) { 
                        super.handleMessage(msg);
                        if (msg.what == 0x120) { 
                            int upper = msg.getData().getInt(UPPER_NUM);
                            ArrayList<Integer> nums = new ArrayList<Integer>();
                            // 计算从2开始、到upper的所有质数
                            outer:
                            for (int i = 2; i <= upper; i++) { 
                                // 用i处于从2开始、到i的平方根的所有数
                                for (int j = 2; j <= Math.sqrt(i); j++) { 
                                    // 如果可以整除，表明这个数不是质数
                                    if (i != 2 && i % j == 0) { 
                                        continue outer;
                                    }
                                }
                                nums.add(i);
                            }
                            Log.d("Handler.class", "质数分别为：" + nums.toString());
                            Message message = new Message();
                            message.what = 0x110;
                            Bundle bundle = new Bundle();
                            bundle.putIntegerArrayList("Result", nums);
                            message.setData(bundle);
                            mainHandler.sendMessage(message);
                        }
                    }
                };
                Looper.loop();
            }
        }
    
        @Override
        protected void onCreate(@Nullable Bundle savedInstanceState) { 
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_headle);
            mEtNum = findViewById(R.id.etNum);
            mTest = findViewById(R.id.test);
            calThread = new CalThread();
            // 启动新线程
            calThread.start();
            mainHandler = new Handler() { 
                @Override
                public void handleMessage(@NonNull Message msg) { 
                    super.handleMessage(msg);
                    if (msg.what == 0x110) { 
                        Bundle bundles = new Bundle();
                        bundles = msg.getData();
                        ArrayList<Integer> nums = bundles.getIntegerArrayList("Result");
                        mTest.setText("指数为：" + nums.toString());
                    }
                }
            };
        }
    
        // 为按钮的点击事件提供事件处理函数
        public void cal(View view) { 
            // 创建消息
            Message msg = new Message();
            msg.what = 0x120;
            Bundle bundle = new Bundle();
            bundle.putInt(UPPER_NUM, Integer.parseInt(mEtNum.getText().toString()));
            msg.setData(bundle);
            // 向新线程中的Handler发送消息
            calThread.mHandler.sendMessage(msg);
        }
    }

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDQ5NTY3OA_size_16_color_FFFFFF_t_70]  
3、在子线程中发送，在主线程中接收，在子线程中处理，在主线程中更新  
（1）在UI中创建自定义的Handler对象  
（2） 设置按钮的点击监听事件，点击按钮之后，会启动一个线程  
（3） 线程启动后，Handler对象会获取一个Message，设置Message的obj属性为“更改后的内容”，然后将Message发送出去  
（4）在自定义的Handler中，实现了handleMessage方法，在这个方法中，我们接收到message，然后将message中的obj取出，更新TextView。

public class testActivity extends Activity { 
        private TextView mTVOriginal;
        private EditText mETInput;
        private Button mBtnModify;
    
        @Override
        protected void onCreate(@Nullable Bundle savedInstanceState) { 
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_test);
            initView();
        }
    
        private void initView() { 
            mTVOriginal = findViewById(R.id.original);
            mETInput = findViewById(R.id.etInput);
            mBtnModify = findViewById(R.id.btnModify);
    
            mBtnModify.setOnClickListener(new View.OnClickListener() { 
                @Override
                public void onClick(View v) { 
                    Thread thread = new MyThread();
                    thread.start();
                }
            });
        }
    
        class MyThread extends Thread { 
            @Override
            public void run() { 
                super.run();
                String str = "***" + mETInput.getText().toString() + "***";
                Message msg = handler.obtainMessage();
                msg.obj = str;
                handler.sendMessage(msg);
                Log.d("子线程", "这里是发送消息的线程，发送的内容是：" + str + " 线程名是：" + Thread.currentThread().getName());
            }
        }
    
        Handler handler = new Handler() { 
            @Override
            public void handleMessage(@NonNull Message msg) { 
                super.handleMessage(msg);
                String sttr = (String) msg.obj;
                mTVOriginal.setText(sttr);
                Log.d("主线程", "这里是更改UI的线程，接收到的内容是：" + sttr + " 线程名是：" + Thread.currentThread().getName());
            }
        };
    }

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDQ5NTY3OA_size_16_color_FFFFFF_t_70 1]  
运行后，结果如下所示：  
![在这里插入图片描述][20210527104303934.png]  
![在这里插入图片描述][20210527110004436.png]  
4、 点击按钮，开始播放幻灯片。

/** * 实现点击按钮，开始播放幻灯片，每张幻灯片间隔1s */
    public class HandlerActivity extends Activity { 
        private ImageView imagChange;
        private Button mBtnStart;
        // 定义切换的图片数组id
        int imgids[] = new int[]{ 
                R.drawable.ic_pikachu1, R.drawable.ic_pikachu2,
                R.drawable.ic_pikachu3, R.drawable.ic_pikachu4
        };
        int imgIndex = 0;
    
        @Override
        protected void onCreate(@Nullable Bundle savedInstanceState) { 
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_handler);
            initView();
        }
    
        private void initView() { 
            imagChange = findViewById(R.id.img);
            mBtnStart = findViewById(R.id.btnStart);
    
            mBtnStart.setOnClickListener(new View.OnClickListener() { 
                @Override
                public void onClick(View v) { 
                    Thread thread = new MyThread();
                    thread.start();
                }
            });
        }
    
        class MyThread extends Thread { 
            @Override
            public void run() { 
                super.run();
                while (true) { 
                    Object obj = new Object();
                    synchronized (obj) { 
                        Message msg = handler.obtainMessage();
                        msg.obj = imgIndex;
                        handler.sendMessage(msg);
                        imgIndex++;
                        try { 
                            Thread.sleep(1 * 1000);
                        } catch (InterruptedException e) { 
                            e.printStackTrace();
                        }
                        if (imgIndex >= imgids.length) { 
                            imgIndex = 0;
                        }
                    }
                }
            }
        }
    
        Handler handler = new Handler() { 
            @Override
            //重写handleMessage方法,根据msg中what的值判断是否执行后续操作
            public void handleMessage(@NonNull Message msg) { 
                super.handleMessage(msg);
                int i = (int) msg.obj;
                BitmapDrawable bd = (BitmapDrawable) imagChange.getDrawable();
                if (bd != null && !bd.getBitmap().isRecycled()) { 
                    bd = null;
                }
                imagChange.setImageResource(imgids[i]);
            }
        };
    }

[20210524160910534.png]: /images/20221014/11d8e93f197445d4bd124c53d13df816.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDQ5NTY3OA_size_16_color_FFFFFF_t_70]: /images/20221014/eabed8fab73c48f8b46c23e6a9ab2ed4.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDQ5NTY3OA_size_16_color_FFFFFF_t_70 1]: /images/20221014/1c62a0a53cdc4927b1516bfa14438c76.png
[20210527104303934.png]: /images/20221014/e1ac785c6c774e11b10ec56fb71a71ab.png
[20210527110004436.png]: /images/20221014/399684bd816e47c99aea8a80843bcb8a.png