Android:Unit3
控制元件
TextView
<TextView android:layout_width="match_parent" android:layout_height="wrap_content" android:id="@+id/text_view" android:text="textView,test 成功" // 文字 android:gravity="center" // 文字居左、右、上、下 android:textSize="24sp" // 文字大小 android:textColor="#000" // 文字顏色 tools:ignore="MissingConstraints" />
Button
Activity中:
Button button = findViewById(R.id.button); button.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { Toast.makeText(ControlActivity.this,"按鈕啟動",Toast.LENGTH_SHORT).show();; } });
res中:
<Button android:id="@+id/button" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_marginTop="76dp" android:text="按鈕Button" android:textAllCaps="false" // 大小寫分辨 " />
EditText
Activity中:
Button button = findViewById(R.id.button);
final EditText editText = findViewById(R.id.edit_text);
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// 獲取editText的資訊
Toast.makeText(ControlActivity.this,editText.getText().toString(),Toast.LENGTH_SHORT).show();;
}
});
res中:
<EditText
android:id="@+id/edit_text"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="預設提示" // 預設提示符
android:maxLines="2" // 最多佔2行
/>
ImageView
Activity中:
更換影象
imageView.setImageResource(R.drawable.banana_pic);
res中:
<ImageView
android:id="@+id/image_view"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="@drawable/apple_pic" // 新增圖片地址
/>
PragressBar
Activity中:
使用setVisibility可以傳入
View.VISIBLE(預設,可見)
View.INVISIBLE(不可見,佔據位置和大小)
View.GONE(不可見,不佔據空間)
if (progressBar.getVisibility() == View.GONE) {
progressBar.setVisibility(View.VISIBLE);
} else {
progressBar.setVisibility(View.GONE);
}
// 設定進度條
int pro = progressBar.getProgress();
pro = pro + 10;
progressBar.setProgress(pro);
res中:
<ProgressBar
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/progress_bar"
style="?android:attr/progressBarStyleHorizontal" // 以進度條方式開啟
android:max="100" // 進度條最大值100
/>
AlertDialog
Activity中:
AlertDialog.Builder dialog = new AlertDialog.Builder(ControlActivity.this);
dialog.setTitle("This is Dialog");
dialog.setMessage("something Important");
dialog.setCancelable(false); // 可否取消
dialog.setPositiveButton("ok", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
}
});
dialog.setNegativeButton("cancel", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
}
});
dialog.show();
res中:
ProgressDialog
Activity中:
ProgressDialog progressDialog = new ProgressDialog(ControlActivity.this);
progressDialog.setTitle("this is proDialog");
progressDialog.setMessage("loading ...");
progressDialog.setCancelable(true); // 是否可以back消除。如果否,呼叫ProgressDialog的dismiss()關閉對話方塊,否則一直存在
progressDialog.show();
res中:
ListView
1. 基本ListView
Activity中:
// 首先將需要載入的資料放入data中
private String[] data = {"Apple","Banana","orange","Watermelon",
"Pear","Grape","Pineapple","Strawberry","Cherry","Mango","Apple",
"Banana","Orange","Watermelon","Pear","Grape","Pineapple","Strawberry",
"Cherry","Mango"};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// 配置介面卡:(context,子項佈局id(listView的佈局,類似容器),資料);這裡將data放入了item_1中
ArrayAdapter<String> adapter = new ArrayAdapter<String>(
MainActivity.this, android.R.layout.simple_expandable_list_item_1,
data);
// listView裝載
ListView listView = findViewById(R.id.list_view);
listView.setAdapter(adapter);
}
res.main_layout中:
新增ListView控制元件
<ListView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/list_view"/>
2. 自定義ListView
Activity中:
主Activity中使用自定義的Fruit介面卡
public class Main2Activity extends AppCompatActivity {
private List<Fruit> fruitList = new ArrayList<>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main2);
initFruits();
FruitAdapter adapter = new FruitAdapter(Main2Activity.this, R.layout.fruit_item, fruitList);
ListView listView = findViewById(R.id.list_view2);
listView.setAdapter(adapter);
}
private void initFruits() {
for(int i = 0; i < 2; i++) {
Fruit apple = new Fruit("Apple", R.drawable.apple_pic);
fruitList.add(apple);
Fruit banana = new Fruit("Banana", R.drawable.banana_pic);
fruitList.add(banana);
Fruit watermelon = new Fruit("Watermelon", R.drawable.watermelon_pic);
fruitList.add(watermelon);
Fruit pear = new Fruit("Pear", R.drawable.pear_pic);
fruitList.add(pear);
Fruit grape = new Fruit("Grape", R.drawable.grapes_pic);
fruitList.add(grape);
Fruit strawberry = new Fruit("Strawberry", R.drawable.strawberry_pic);
fruitList.add(strawberry);
Fruit cherry = new Fruit("Cherry", R.drawable.cherry_pic);
fruitList.add(cherry);
Fruit mango = new Fruit("Mango", R.drawable.mango_pic);
fruitList.add(mango);
}
}
}
自定義Fruit介面卡
/**
* 自定義介面卡
*/
public class FruitAdapter extends ArrayAdapter<Fruit> {
private int resourceId;
public FruitAdapter(@NonNull Context context, int resource, @NonNull List<Fruit> objects) {
super(context, resource, objects);
resourceId = resource;
}
@Override
public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
// 為子項載入傳入的佈局
// layoutInflater的from可以構建layoutInflater物件
// inflate可以動態載入佈局(要載入佈局的id,給載入好的佈局再新增一個父佈局)
// 第三個引數(只讓在父佈局中宣告layout屬性生效,但不為View新增父佈局,因為一旦View有了父佈局,不能再新增到ListView中)
View view = LayoutInflater.from(getContext()).inflate(resourceId, parent, false);
TextView fruitName = view.findViewById(R.id.fruit_name);
ImageView fruitImage = view.findViewById(R.id.fruit_image);
Fruit fruit = getItem(position); // 獲取當前項的Fruit例項
fruitName.setText(fruit.getName());
fruitImage.setImageResource(fruit.getImageId());
return view;
}
自定義Fruit類
public class Fruit {
private String name;
private int imageId;
public Fruit(String name, int imageId) {
this.name = name;
this.imageId = imageId;
}
public String getName() {
return name;
}
public int getImageId() {
return imageId;
}
}
res.layout中:
/
<ListView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/list_view2"/>
fruit_layout中:
新建一個fruit_layout,對應fruit中的佈局
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/fruit_image"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/fruit_name"
android:layout_gravity="center_vertical"
android:layout_marginLeft="10dp"/>
3. 優化ListView
每次載入getView()都重新載入一次佈局,可以使用convertView引數,將之前載入的佈局進行快取。
@Override
public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
View view;
ViewHolder viewHolder;
if (convertView == null) {
view = LayoutInflater.from(getContext()).inflate(resourceId, parent, false);
viewHolder = new ViewHolder();
viewHolder.fruitName = view.findViewById(R.id.fruit_name);
viewHolder.fruitImage = view.findViewById(R.id.fruit_image);
view.setTag(viewHolder); // 將ViewHolder儲存在View中
} else {
view = convertView;
viewHolder = (ViewHolder) view.getTag(); // 重新獲取ViewHolder
}
Fruit fruit = getItem(position);
viewHolder.fruitImage.setImageResource(fruit.getImageId());
viewHolder.fruitName.setText(fruit.getName());
return view;
}
class ViewHolder {
ImageView fruitImage;
TextView fruitName;
}
解決了重複載入佈局的問題,但每次getView()方法中還是會呼叫View的findViewById()獲取一次控制元件例項。
新增一個內部類ViewHolder,用於對控制元件例項進行快取。當convertView為空時,建立一個ViewHolder物件,並將控制元件的例項都存放在ViewHolder裡,然後呼叫View的setTag()方法,將ViewHolder物件存在View中。
如果不為空,呼叫View.getTag(),把ViewHolder取出來。控制元件例項都在快取中存取。
4. ListView點選事件
Actibity中:
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
Fruit fruit = fruitList.get(position); // 通過position判斷使用者點選的哪個子項
Toast.makeText( Main2Activity.this,fruit.getName(),Toast.LENGTH_SHORT).show();
}
});
RecyclerView
佈局
1.LinearLayout
2.FrameLayout
3.RelativeLayout
4.PercentLayout
自定義
1.引入佈局
Activity中:
隱藏預設標題欄
ActionBar actionBar = getSupportActionBar(); // 隱藏標題欄
if (actionBar != null) {
actionBar.hide();
}
res.layout中:
新建自定義title佈局
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#000">
<!-- 自定義新的標題框-->
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/button1"
android:text="返回"
android:background="#C21B1B"
android:layout_margin="5dp"
/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/text"
android:text="Hello Text"
android:background="#0C0C0C"
android:textColor="#fff"
android:layout_weight="1"
android:gravity="center"
/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/button2"
android:text="進入"
android:background="#4CAF50"
android:layout_margin="5dp"
/>
</LinearLayout>
res.main_layout中:
<include layout="@layout/title"/>
2.自定義控制元件
Activity中:
新建TitleLayout類繼承LearnLayout
/**
* Title佈局,繼承自LinearLayout
*/
public class TitleLayout extends LinearLayout {
public TitleLayout(Context context, @Nullable AttributeSet attrs) {
super(context, attrs);
// 將此佈局新增到title_layout中
// from()方法,建立LayoutInflater物件
// inflate(int,Root)要載入佈局的id,載入好的佈局新增父佈局
LayoutInflater.from(context).inflate(R.layout.title,this);
Button button1 = findViewById(R.id.button1);
button1.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
Activity context1 = (Activity) getContext(); // getContext()獲取當前執行的上下文,強轉成Activity
context1.finish();
}
});
Button button2 = findViewById(R.id.button2);
button2.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
Toast.makeText(getContext(),"進入介面成功",Toast.LENGTH_SHORT).show();
}
});
}
}
res.main_layout中:
使用TitleLayout。此時功能和
相同,但是是以控制元件方式新增,還為控制元件添加了點選事件
<com.example.unit3_3_self.TitleLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
tools:ignore="MissingConstraints"
/>