Integrate Paypal in Android Application

First Create New Android Project and then Add below Code.

MainActivity.java

public class PizzaMain extends Activity implements OnClickListener {
  /** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);

PayPal ppObj = PayPal.initWithAppID(this.getBaseContext(), "APP-80W284485P519543T", PayPal.ENV_NONE);

CheckoutButton launchPayPalButton = ppObj.getCheckoutButton(this, PayPal.BUTTON_152x33, CheckoutButton.TEXT_PAY);
  RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);

  params.addRule(RelativeLayout.CENTER_HORIZONTAL);

launchPayPalButton.setLayoutParams(params);
launchPayPalButton.setOnClickListener(this);

((RelativeLayout) findViewById(R.id.mRlayout1)).addView(launchPayPalButton);
    }

@Override
public void onClick(View v) {
// TODO Auto-generated method stub
PayPalPayment newPayment = new PayPalPayment();
char val[] = { '5', '0' };
BigDecimal obj_0 = new BigDecimal(val);
newPayment.setSubtotal(obj_0);
newPayment.setCurrencyType("USD");
newPayment.setRecipient("my@email.com");
newPayment.setMerchantName("My Company");
Intent paypalIntent = PayPal.getInstance().checkout(newPayment, this);
this.startActivityForResult(paypalIntent, 1);
}

@SuppressWarnings("unused")
@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
switch (resultCode) {
case Activity.RESULT_OK:
// The payment succeeded
String payKey = data.getStringExtra(PayPalActivity.EXTRA_PAY_KEY);
// Tell the user their payment succeeded
break;
case Activity.RESULT_CANCELED:
// The payment was canceled
// Tell the user their payment was canceled
break;
case PayPalActivity.RESULT_FAILURE:
// The payment failed -- we get the error from the EXTRA_ERROR_ID
// and EXTRA_ERROR_MESSAGE
String errorID = data.getStringExtra(PayPalActivity.EXTRA_ERROR_ID);
String errorMessage = data.getStringExtra(PayPalActivity.EXTRA_ERROR_MESSAGE);
// Tell the user their payment was failed.
               break;
       }
   }
}

And Give below permissions into your AndroidManifest.xml file.

<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.READ_PHONE_STATE"/>

And Add Activity into your AndroidManifest.xml file.

<activity
    android:name="com.paypal.android.MEP.PayPalActivity"
    android:configChanges="keyboardHidden|orientation"
    android:theme="@android:style/Theme.Translucent.NoTitleBar" />

Add PayPal_MPL.jar Jar File as a Refrence Library into Your application

Enjoy :-)

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