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法律研究如何在 Android 中使用 Picasso
本示例演示如何使用 Picasso
步骤 1 − 在 Android Studio 中新建一个项目，转到文件 ⇒ 新建项目，填写所有必需信息来新建一个项目。
步骤 2 − 添加以下代码到 res/layout/activity_main.xml。
<?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:id="@+id/activity_main" android:layout_width="match_parent" android:layout_height="match_parent" android:padding="16dp" tools:context=".MainActivity"> <Button android:id="@+id/btnDrawable" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignParentStart="true" android:layout_centerVertical="true" android:text="Drawable" /> <ImageView android:id="@+id/imageView" android:layout_width="200dp" android:layout_height="200dp" android:layout_centerHorizontal="true" android:src="@mipmap/ic_launcher" /> <Button android:id="@+id/btnPlaceholder" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignBaseline="@+id/btnUrl" android:layout_alignBottom="@+id/btnUrl" android:layout_centerHorizontal="true" android:text="Placeholder" /> <Button android:id="@+id/btnUrl" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignBaseline="@+id/btnDrawable" android:layout_alignBottom="@+id/btnDrawable" android:layout_alignParentEnd="true" android:text="URL" /> <Button android:id="@+id/btnError" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_below="@+id/btnDrawable" android:layout_alignParentStart="true" android:layout_marginTop="12dp" android:text="Error" /> <Button android:id="@+id/btnCallBack" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignBaseline="@+id/btnError" android:layout_alignStart="@+id/btnPlaceholder" android:layout_alignBottom="@+id/btnError" android:text="Callback" /> <Button android:id="@+id/btnResize" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignBaseline="@+id/btnCallBack" android:layout_alignBottom="@+id/btnCallBack" android:layout_alignParentEnd="true" android:text="Resize" /> <Button android:id="@+id/btnRotate" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_below="@+id/btnError" android:layout_alignParentStart="true" android:layout_marginTop="12dp" android:text="Rotate" /> <Button android:id="@+id/btnScale" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignStart="@+id/btnCallBack" android:layout_alignBottom="@+id/btnTarget" android:text="Scale" /> <Button android:id="@+id/btnTarget" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignBaseline="@+id/btnRotate" android:layout_alignBottom="@+id/btnRotate" android:layout_alignParentEnd="true" android:text="Targets" /> </RelativeLayout>
步骤 3 − 添加以下代码到 src/MainActivity.java
package app.com.sample;
import androidx.appcompat.app.AppCompatActivity;
import android.graphics.Bitmap;
import android.graphics.drawable.Drawable;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.Toast;
import com.squareup.picasso.Callback;
import com.squareup.picasso.Picasso;
import com.squareup.picasso.Target;
public class MainActivity extends AppCompatActivity implements View.OnClickListener {
ImageView imageView;
int i = 0;
Button btnDrawableImage, btnUrlImage, btnErrorImage, btnPlaceholderImage, btnCallback, btnResizeImage,
btnRotateImage, btnScaleImage, btnTarget;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initView();
}
private void initView() {
imageView = findViewById(R.id.imageView);
btnDrawableImage = findViewById(R.id.btnDrawable);
btnUrlImage = findViewById(R.id.btnUrl);
btnPlaceholderImage = findViewById(R.id.btnPlaceholder);
btnErrorImage = findViewById(R.id.btnError);
btnCallback = findViewById(R.id.btnCallBack);
btnResizeImage = findViewById(R.id.btnResize);
btnRotateImage = findViewById(R.id.btnRotate);
btnScaleImage = findViewById(R.id.btnScale);
btnTarget = findViewById(R.id.btnTarget);
btnDrawableImage.setOnClickListener(this);
btnPlaceholderImage.setOnClickListener(this);
btnUrlImage.setOnClickListener(this);
btnCallback.setOnClickListener(this);
btnResizeImage.setOnClickListener(this);
btnErrorImage.setOnClickListener(this);
btnRotateImage.setOnClickListener(this);
btnScaleImage.setOnClickListener(this);
btnTarget.setOnClickListener(this);
}
@Override
public void onClick(View view) {
switch (view.getId()) {
case R.id.btnDrawable:
Picasso.with(this).load(R.drawable.image).into(imageView);
break;
case R.id.btnPlaceholder:
Picasso.with(this).load("www.journaldev.com").placeholder(R.drawable.placeholder).into(imageView);
break;
case R.id.btnUrl:
Picasso.with(this).load("http://cdn.journaldev.com/wp-content/uploads/2017/01/android- constraintlayout-sdk-tool-install.png").placeholder(R.drawable.placeholder).into(imageView);
break;
case R.id.btnError:
Picasso.with(this).load("www.journaldev.com").placeholder(R.drawable.placeholder).error(R.drawable.
error).into(imageView);
break;
case R.id.btnCallBack:
Picasso.with(this).load("www.journaldev.com").error(R.mipmap.ic_launcher).into(imageView, new Callb ack() {
@Override
public void onSuccess() {
Log.d("TAG", "onSuccess");
}
@Override
public void onError() {
Toast.makeText(getApplicationContext(), "An error occurred", Toast.LENGTH_SHORT).show();
}
});
break;
case R.id.btnResize:
Picasso.with(this).load(R.drawable.image).resize(200, 200).into(imageView);
break;
case R.id.btnRotate:
Picasso.with(this).load(R.drawable.image).rotate(90f).into(imageView);
break;
case R.id.btnScale:
if (i == 3)
i = 0;
else {
if (i == 0) {
Picasso.with(this).load(R.drawable.image).fit().into(imageView);
Toast.makeText(getApplicationContext(), "Fit", Toast.LENGTH_SHORT).show();
}
else if (i == 1) {
Picasso.with(this).load(R.drawable.image).resize(200, 200).centerCrop().into(imageView);
Toast.makeText(getApplicationContext(), "Center Crop", Toast.LENGTH_SHORT).show();
}
else if (i == 2) {
Picasso.with(this).load(R.drawable.image).resize(200, 200).centerInside().into(imageView);
Toast.makeText(getApplicationContext(), "Center Inside", Toast.LENGTH_SHORT).show();
}
i++;
}
break;
case R.id.btnTarget:
Picasso.with(this).load("http://cdn.journaldev.com/wp-content/uploads/2017/01/android- constraintlayout-sdk-tool- install.png").placeholder(R.drawable.placeholder).error(R.drawable.error).into(target);
break;
}
}
private Target target = new Target() {
@Override
public void onBitmapLoaded(Bitmap bitmap, Picasso.LoadedFrom from) {
imageView.setImageBitmap(bitmap);
}
@Override
public void onBitmapFailed(Drawable errorDrawable) {
imageView.setImageDrawable(errorDrawable);
}
@Override
public void onPrepareLoad(Drawable placeHolderDrawable) {
imageView.setImageDrawable(placeHolderDrawable);
}
};
}步骤 4 − 添加以下代码到 androidManifest.xml
<?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="app.com.sample"> <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/> <application android:allowBackup="true" android:icon="@mipmap/ic_launcher" android:label="@string/app_name" android:roundIcon="@mipmap/ic_launcher_round" android:supportsRtl="true" android:theme="@style/AppTheme"> <activity android:name=".MainActivity"> <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> </application> </manifest>
我们来尝试运行你的应用程序。我假设你已经将你的真机与电脑连接。要在 android studio 中运行应用程序，打开一个项目中的 activity 文件，点击工具栏中的运行
图标。选择你的移动设备作为选项，然后检查你的移动设备上显示的默认屏幕 −
更新时间： 07-Jul-2020
189 次浏览
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