LiveData败许，當(dāng)數(shù)據(jù)改變時(shí)可被觀察到，同時(shí)具有生命感知能力芭析，該能力是由于其內(nèi)部類LifecycleBoundObserver繼承了GenericLifecycleObserver->LifecycleEventObserver->LifecycleObserver。
關(guān)鍵代碼：

observe(LifecycleOwner owner, Observer<? super T> observer) {
  LifecycleBoundObserver wrapper = new LifecycleBoundObserver(owner, observer);
  ...
  owner.getLifecycle().addObserver(wrapper);
}

當(dāng)組件（如：Activity）生命周期狀態(tài)改變時(shí)，會(huì)移除observer，所以也就不會(huì)發(fā)生內(nèi)存泄漏。也不用手動(dòng)處理生命周期。

        public void onStateChanged(LifecycleOwner source, Lifecycle.Event event) {
            if (mOwner.getLifecycle().getCurrentState() == DESTROYED) {
                removeObserver(mObserver);
                return;
            }
            activeStateChanged(shouldBeActive());
        }

使用：
LiveData通常放在ViewModel中废菱，由ViewModel管理LiveData技矮。

import androidx.lifecycle.MutableLiveData;
import androidx.lifecycle.ViewModel;

public class NameViewModel extends ViewModel {
    MutableLiveData<String> name;

    public MutableLiveData<String> getName() {
        if (name == null) {
            name = new MutableLiveData<>();
        }
        return name;
    }
}

在Activity中，觀察LiveData的改變

import android.os.Bundle;
import android.view.View;
import android.widget.TextView;

import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import androidx.lifecycle.Observer;
import androidx.lifecycle.ViewModelProvider;

public class LiveDataActivity extends AppCompatActivity {
    NameViewModel nameViewModel;
    private TextView tvName;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_live_data);
        nameViewModel = new ViewModelProvider(this, new ViewModelProvider.NewInstanceFactory())
                .get(NameViewModel.class);
        nameViewModel.getName().observe(this, new Observer<String>() {
            @Override
            public void onChanged(String s) {
                //改變LiveData的值后殊轴，會(huì)被觀察到衰倦，從而改變tvName的值
                tvName.setText(s);
            }
        });
        nameViewModel.getName().setValue("Android");
        tvName = findViewById(R.id.tvName);
        findViewById(R.id.btnChangeName).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //改變LiveData的值
                nameViewModel.getName().setValue("Google");
            }
        });
    }
}

當(dāng)LiveData值改變時(shí)，TextView的內(nèi)容也隨之改變旁理。