WD的Activity学习
2018-11-04 本文已影响0人
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大多为《第一行代码代码》内容
1. Menu用法
[1] 在Menu目录下定义main.xml文件
<menu xmlns:android="http://schemas.android.com/apk/res/android">
<item
android:id="@+id/add_item"
android:title="Add"></item>
<item
android:id="@+id/remove_item"
android:title="Remove"></item>
</menu>
[2] 重写onCreateOptionsMenu()，使用inflate导入main.xml
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.main,menu);
return true;
}
[3] 重写onOptionsItemSelected()，写入点击事件
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case R.id.add_item:
Toast.makeText(FirstActivity.this,"you clicked add",Toast.LENGTH_LONG).show();
break;
case R.id.remove_item:
Toast.makeText(FirstActivity.this,"you clicked remove",Toast.LENGTH_LONG).show();
break;
default:
}
return true;
}
2. 显式启动和隐式启动
[1] 显式 new Intent(A.this,B.class)
Intent intent = new Intent(FirstActivity.this,SecondActivity.class);
startActivity(intent);
[2] 隐式 manifest中通过intent-filter 定义属性action和category来确定Activity
<intent-filter>
<action android:name="type.anything"></action>
<category android:name="android.intent.category.DEFAULT"></category>
</intent-filter>
Intent intent1 = new Intent("type.anything");
startActivity(intent1);
顾名思义，显式可以在代码中看到切换的Activity,隐式要和intent-filter匹配才能跳转
3. Activity间数据的传递
[1] 传递给下一个Activity
intent.putExtra("data","data_return");
Intent intent = getIntent();
mString = intent.getStringExtra("data");
[2] 返回数据给上一个Activity
- A: startActivityForResult() 启动下一个Activity
startActivityForResult(intent,1);
onActivityResult() 处理返回的数据
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
switch (requestCode) {
case 1:
if(resultCode == RESULT_OK) {
String string = data.getStringExtra("data");
Toast.makeText(FirstActivity.this,string,Toast.LENGTH_SHORT).show();
Log.e("FirstActivity", "onActivityResult: "+string);
}
break;
default:
}
}
- B: setResult() 放入返回给A的数据,通常要重写onBackPressedzhon
public void onBackPressed() {
Intent intent = new Intent();
intent.putExtra("data","data_return");
setResult(RESULT_OK,intent);
finish();
}
4. Activity数据的保存
[1] 重写onSaveInstanceState() 方法
@Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
String tempData = "something just typed";
outState.putString("temp",tempData);
}
[2] 在onCreate()中判断savedInstanceState != null，并取出数据
if(savedInstanceState != null) {
String tempData = savedInstanceState.getString("temp");
}
5. Activity启动方式
[1] Standard
[2] singleTop
[3] singTask
[4] singleInstance
6. Activity生命周期
[1] onCreate→onStart→onResume→onPause→onStop→onDestroy
[2] A跳转到B的过程：
A.onPause→B.onCreate→B.onStart→B.onResume →A.onStop
[3] 总是成对出现的方法： resume 和pause
