3.2 常用控件的使用方法

TextView

用于在界面上显示一段文本信息

    <TextView
        android:id="@+id/text_view"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:textSize="24sp"
        android:textColor="#000000"
        android:text="Hello World!" />

Button

用于和用户进行交互，最后一项是使按钮名不再默认大写

    <Button
        android:id="@+id/button"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Button01"
        android:textAllCaps="false" />

为Button的点击事件注册一个监听器

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main_layout);
        Button button = (Button) findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener(){
            @Override
            public void onClick(View v) {

            }
        });
    }
}

EditText

允许用户在控件里输入和编辑内容

• hint显示一段提示性文本，当输入任何内容时，这段文本自动消失
• maxline指定了EditText的最大行数为两行，当输入的内容超过两行时，文本就会向上滚动，而EditText则不会继续拉伸

    <EditText
        android:id="@+id/edit_text"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="Type something here"
        android:maxLines="2" />

EditText与Button结合

点击按钮来获取EditText中输入的内容：

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    private EditText editText;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main_layout);
        Button button = (Button) findViewById(R.id.button);
        editText=(EditText)findViewById(R.id.edit_text); 
        button.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.button:
                String inputText = editText.getText().toString();
                Toast.makeText(MainActivity.this, inputText, Toast.LENGTH_SHORT).show();
                break;
            default:
                break;
        }
    }
}

ImageView

用于在界面上展示图片

在res目录下新建一个drawable-xhdpi目录，然后将事先准备好的两张图片img_1.png和imag_2.png复制到该目录下

    <ImageView
        android:id="@+id/image_view"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:src="@drawable/img_1" />

通过代码动态地更改（点击按钮切换图片）ImageView中的图片：

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    //private EditText editText;
    private ImageView imageView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main_layout);
        Button button = (Button) findViewById(R.id.button);
        //editText=(EditText)findViewById(R.id.edit_text);
        imageView=(ImageView)findViewById(R.id.image_view);
        button.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.button:
                //String inputText = editText.getText().toString();
                //Toast.makeText(MainActivity.this, inputText, Toast.LENGTH_SHORT).show();
                imageView.setImageResource(R.drawable.img_2);
                break;
            default:
                break;
        }
    }
}

ProgressBar

用于在界面上显示一个进度条

圆形进度条：

    <ProgressBar
        android:id="@+id/progress_bar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

点击按钮，能看到进度条会在显示与隐藏之间来回切换

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    //private EditText editText;
    private ImageView imageView;
    private ProgressBar progressBar;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main_layout);
        Button button = (Button) findViewById(R.id.button);
        //editText=(EditText)findViewById(R.id.edit_text);
        imageView=(ImageView)findViewById(R.id.image_view);
        progressBar = (ProgressBar) findViewById(R.id.progress_bar);
        button.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.button:
                //String inputText = editText.getText().toString();
                //Toast.makeText(MainActivity.this, inputText, Toast.LENGTH_SHORT).show();
                imageView.setImageResource(R.drawable.img_2);
                if (progressBar.getVisibility() == View.GONE) {
                    progressBar.setVisibility(View.VISIBLE);
                } else {
                    progressBar.setVisibility(View.GONE);
                }
                break;
            default:
                break;
        }
    }
}

水平进度条：最大值为100

    <ProgressBar
        android:id="@+id/progress_bar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        style="?android:attr/progressBarStyleHorizontal"
        android:max="100" />

每点击一次按钮，会在现有的进度上加10

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    //private EditText editText;
    private ImageView imageView;
    private ProgressBar progressBar;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main_layout);
        Button button = (Button) findViewById(R.id.button);
        //editText=(EditText)findViewById(R.id.edit_text);
        imageView=(ImageView)findViewById(R.id.image_view);
        progressBar = (ProgressBar) findViewById(R.id.progress_bar);
        button.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.button:
                //String inputText = editText.getText().toString();
                //Toast.makeText(MainActivity.this, inputText, Toast.LENGTH_SHORT).show();
                imageView.setImageResource(R.drawable.img_2);
                int progress = progressBar.getProgress();
                progress=progress+10;
                progressBar.setProgress(progress);
                break;
            default:
                break;
        }
    }
}

AlertDialog

在当前的界面弹出一个对话框，这个对话框是置顶于所有界面元素之上的，能够屏蔽掉其他控件的交互能力，用于提示一些非常重要的内容或者警告信息

点击按钮就会弹出窗口

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    //private EditText editText;
    private ImageView imageView;
    private ProgressBar progressBar;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main_layout);
        Button button = (Button) findViewById(R.id.button);
        //editText=(EditText)findViewById(R.id.edit_text);
        imageView=(ImageView)findViewById(R.id.image_view);
        progressBar = (ProgressBar) findViewById(R.id.progress_bar);
        button.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.button:
                AlertDialog.Builder dialog = new AlertDialog.Builder(MainActivity.this);
                dialog.setTitle("This is Dialog");
                dialog.setMessage("Someting important.");
                dialog.setCancelable(false);
                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();
                break;
            default:
                break;
        }
    }
}

ProgressDialog

和AlertDialog类似，可以在界面上弹出一个对话框，能够屏蔽掉其他控件的交互能力，但会在对话框中显示一个进度条，一般用于表示当前操作比较耗时，让用户耐心等待。

如果在setCancelable()中传入了false，表示ProgressDialog是不能通过back键取消掉的，当数据加载完成后可以调用ProgressDialog的dismiss()方法来关闭对话框，否则ProgressDialog将会一直存在。

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    //private EditText editText;
    private ImageView imageView;
    private ProgressBar progressBar;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main_layout);
        Button button = (Button) findViewById(R.id.button);
        //editText=(EditText)findViewById(R.id.edit_text);
        imageView=(ImageView)findViewById(R.id.image_view);
        progressBar = (ProgressBar) findViewById(R.id.progress_bar);
        button.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.button:
                ProgressDialog progressDialog = new ProgressDialog(MainActivity.this);
                progressDialog.setTitle("This is ProgressDialog");
                progressDialog.setMessage("Loading...");
                progressDialog.setCancelable(true);
                progressDialog.show();
                break;
            default:
                break;
        }
    }
}

以下用到哪些控件？

本文地址：https://blog.csdn.net/Black_Cat_33/article/details/114286153